# How can I prove a word is a noun?

When I read a sentence, I can identify nouns. But now I need to give proof that they are indeed nouns, and that is where it goes wrong. I can think of one or two things sometimes (like combining it with an adjective), but that is not enough proof.

So my question is, how can I prove in multiple ways that the word is actually a noun?

• Comments are not for extended discussion; this conversation has been moved to chat. Please go there to comment: further comments here may be deleted. Feb 25, 2015 at 9:52
• Can you tell us what kind of proof you're looking for? For some people, no amount of direct experience is sufficient to prove to them that they exist. For some people, footprints in mud are acceptable proof that someone walked there, until and unless new evidence comes to light. Are you looking for a mathematical proof from axioms, like Russell & Whitehead's 300-page proof that 1+1=2? Would a simple, common-sense explanation of what a noun is satisfy you? Or are you trying to write a computer program to find the nouns in a sentence? Jun 22, 2017 at 7:12

There is no single syntactic or distributional property of nouns which is sufficient to guarantee the inclusion of an item in the word class.

For most modern grammarians there is a major subcategory of the noun class, the ᴘʀᴏɴᴏᴜɴ, the members of which show slightly different properties and distributions. The remainder of the class can be subdivided into the subcategories of ᴄᴏᴍᴍᴏɴ ɴᴏᴜɴ and ᴘʀᴏᴘᴇʀ ɴᴏᴜɴ. Again, proper nouns have certain properties which mark them out from common nouns. For the purposes of this answer, I am concentrating solely on common nouns. Common nouns may be seen as the central, prototypical members of the noun class.

1. Four core syntactic functions/ grammatical relations

Huddleston & Pullum, 2005, describe four syntactic functions that may be carried out by phrases headed by nouns (including phrases consisting of just one word). Within the clause they function freely as Subjects, Objects and Predicative Complements. Within Preposition Phrase structure they occur freely as Complements. This fact is one aspect of nouns that is shared by all the subcategories of noun. Here are some examples with the common noun dog:

• Dogs bite. (Subject)
• I like dogs. (Direct Object)
• We are dogs. (Predicative Complement)
• I'm not scared of dogs. (Complement of Preposition)

If the word being investigated has one of these functions, or is the head of a phrase carrying out one of these functions then there is a good chance that it is a noun. Notice though, that all of these functions or syntactic roles may be carried out by other words or types of phrase. So having one of these functions is in no way a guarantee of nounship. For example, verbs, finite and non-finite clauses also frequently occur as Subjects:

• Smoking is bad for you. (Verb as subject)
• To err is human. (Verb phrase as Subject)
• That he was continuously late was a problem for us. (Finite clause as Subject)
• For him to do that would be inconvenient. (Non-finite clause as Subject)

A good question at this point might be: why does smoking count as a verb and not a noun here? The answer is that although it is in Subject function, it still retains the syntactic properties of being (a non-finite form of) a verb. For example, this verb can still take a Direct Object:

• Smoking cigarettes is bad for you.

It can still take a preposition phrase as a Modifier or Adjunct (read adverbial) like other verbs:

• Smoking in the morning is bad for you.

It can take an adverb as modifier:

• Smoking quickly is bad for you.

It is clear then that if we are to bother to have parts of speech these need to be separated out from the syntactic role or function that a word may have in a phrase or sentence. (We'll do a more thorough investigation of a case study at the end of the post.)

The syntactic role that a word has may be more or less important depending on what categories are contenders for the word. So for example, adjectives commonly function as Predicative Complements, so if the contending word is in Predicative Complement function, and we are wondering if it's an adjective or a noun, this is not much use to us. However, if we're wondering whether an item is an adverb or a noun, then the fact that the word is a Predicative Complement would be fairly decisive in showing it is a noun. Adverbs generally can't function as Predicative Complements:

• *They are worriedly. (adverb as PC - ungrammatical)
• They are worriers. (noun phrase as PC)

2. Other syntactic roles of common nouns

The prototypical functions described above apply to the whole class of nouns. Common nouns however have other syntactic roles that they often take. In particular nouns in English, as well as appearing as the Heads of Noun Phrases, can also be Modifiers within the Noun Phrase structure.

To illustrate, take any item that may have a wrapper, for example biscuits. We can freely generate the compound noun biscuit wrapper. Now if some mad people start collecting these, they will be biscuit wrapper collectors, where the compound noun biscuit wrapper is modifying collectors. If there were enough of them, these people might form a biscuit wrapper collectors association where you could be a Biscuit Wrapper Collectors Association member, a disgruntled one of whom might leave and become a Biscuit Wrapper Collectors Association member assassinator. You get the picture. Just in the same way that both adjectives and nouns can be Predicative Complements, they both freely function as Modifiers within Noun Phrases. If a word cannot be freely used to modify a common noun, then this word is almost definitely not a common noun (pronouns do not freely modify other nouns, nor are they freely modifiable by other nouns).

Nouns and noun phrases also occur much less freely in other types of syntactic roles. So for example, in the following sentence, the noun phrase every three weeks functions as Adjunct of the verb phrase (I use Huddleston & Pullum's terminology here, where ᴀᴅᴊᴜɴᴄᴛ is a special term for a modifier of a verb phrase. Other grammars use the term Adjunct in the same way that the term ᴍᴏᴅɪғɪᴇʀ is used here, namely for an item which is syntactically extra within any given phrase structure):

• Bob gets his back waxed every three weeks.

The phrase every three weeks here is a Noun Phrase. The head of this phrase is the noun weeks. Although this phrase is an Adjunct, there are no grounds for considering it an Adverb Phrase, nor for considering weeks an adverb. The word weeks here retains all of the properties of nouns discussed elsewhere in this piece. It is this fact that makes it a noun. So, the point here is that although the occurrence of nouns as Adjuncts in Verb Phrases is quite restricted, being an Adjunct does not prevent a word from being a noun, although it may make it statistically less likely to be one.

There are many other functions that nouns can have. For example they can be Modifiers in preposition phrases:

• They were five minutes into the match.

I will not attempt to give a definitive list here - if such a list even exists. Suffice it to say, that if a word has a syntactic role that is known to be performed by nouns, then in order to determine the word class of the item, we need to compare the ability of rival word classes to fulfill that role , and look at other criteria too.

3. Modification

Nouns are prototypically modified by adjectives, but as has been shown they are also very commonly modified by other nouns. However, nouns are rarely if ever modified by adverbs. In the very rare instances where they are, the adverb must necessarily come after the noun and not before it:

• The arrival recently of the plague was going to have disastrous consequences for the farmers.
• *The recently arrival of the plague was going to have disastrous consequences for the farmers. (pre-modification of noun by an adverb - ungrammatical)

If a word is modifiable by an adjective, and not by an adverb then it is very, very likely to be a noun. Adverbs can modify many other types of words and phrase, but they are excluded from pre-modifying nouns.

Nouns are frequently post-modified by other phrases, notably preposition phrases, relative clauses and adjective phrases.

4. Complementation

Many nouns take various complements, such as finite clauses and preposition phrases:

• The knowledge that this will not be done easily.
• My dislike of it.

However, Huddleston & Pullum note that:

... nouns differ from verbs and prepositions in that they do not take objects: I dislike it, but not * my dislike it. (p. 326)

This is one of the factors that rules out smoking from being a noun in the examples further above.

5. Determiners

Certain words occur nearly exclusively in Determinative function in noun phrases. These external dependents of the noun are a good indication of a word being a noun. Here are some examples:

• this patient
• every opportunity

The determiner this in the example above shows that this is the noun patient and not the homonymous adjective. The word every here is a near cast iron guarantee that the word opportunity is a noun. However, not all determiners are as good as others for this job. In particular, the can occur in Determinative function in phrases that have no noun:

• I'll take the blue one and the green.
• the good the bad and the ugly
• the bigger the better

Here we see the occurring with adjectives. Notice that every cannot be used in these ways.

6. Inflection for number

Common nouns usually inflect for number and for case. Typically, plurally inflected nouns take /s/ or /z/ as a suffix represented in the writing by the letter 'S'. If we see a word which seems to have an 'S ending because it is plural, this is a strong indication that the item is a noun. If a word doesn't inflect for number then this may be a sign that it is not a noun. However, we need to be a bit careful. There are many irregular plurals in English:

• teeth
• mice
• data

There are also nouns which are the same in the singular or plural:

• a fish, five hundred fish
• a sheep, two sheep

There are also nouns that end in an 'S' whether they are singular or plural:

• crossroads, means, kennels

There are also nouns that only occur in the plural:

• police, cattle, minutae, odds, doldrums, clothes

There are nouns that only occur in the singular, or are uncountable:

• crockery, luggage, equipment.

What this shows is that the ability for a word to show singular and plural forms with 'S' is useful, but a lack of inflection, or of regular inflection, is not sufficient reason to exclude an item from being a noun.

7. Inflection for case

Common nouns inflect for case. They have two forms. The uninflected form is often called PLAIN CASE. The other case is GENITIVE. The genitive form involves the suffix/clitic /s/ or /z/, represented in the writing as 'S' used in conjunction with an apostrophe:

• people, people's
• woman, woman's
• women, women's
• baboon, baboon's

We need to be a little careful here. First of all, this clitic actually gets appended to noun phrases, not just nouns:

• The woman you like's boyfriend

Here we see this clitic appearing after the noun phrase the woman you like. We should not infer from the writing that like is a noun here! Secondly some phrases without nouns can also take this clitic:

• The blind's access to braille versions of periodicals ...

Here we see the clitic after the phrase the blind. Some writers like Huddleston & Pullum regard the blind here as a noun phrase without a noun. Here we see this clitic attached to an adjective.

8. Negative attributes

Of course, when considering whether a phrase is a noun or some other type of word, it is the properties that another class of words have and that nouns don't, which will provided the decisive data. Importantly, nouns can't function as the head of a main clause. In other words they can't assume the syntactic role of Predicator (the function carried out by the verb).

Another feature of nouns is that they are not gradable, whereas many other adjectives are. Equally it is the property of not being modifiable by adverbs which is crucial for demonstrating that a noun modifying other nouns is still a noun and not an adjective.

There are many other negative criteria we can use to demonstrate that a given word is likely to be or definitely isn't a noun.

9. The pronoun substitution test

It is sometimes posited that a good test to see if an item is a noun is to see whether it can be grammatically replaced with a pronoun. In actual fact, although nouns will often be replaceable with pronouns, more often than not in declarative sentences so will any other phrase in Subject or Object function, or functioning as the Complement of a Preposition:

• 1 a. To err is human.
• 1 b. It is human.
• 2 a. I don't like that you always take the window seat
• 2 b. I don't like it
• 3 a. I'm worried about him eating all the strawberry ones when I'm not looking.
• 3 b. I'm worried about it

None of the items that have been replaced by the pronoun it here is a noun. Notice as well, that pronouns don't 'replace' nouns if the noun has dependents. When we substitute a phrase with a pronoun, the entire noun phrase goes, determiners, modifiers and complements too. In addition we cannnot use this test when a noun has the function of Modifier within a phrase including when they are Adjuncts (- modifiers in verb phrases). The nouns and noun phrases in the following examples cannot be replaced by pronouns:

• three miles away from here
• miles wide
• two days late
• the writer James Joyce
• we went there the day before yesterday

It seems that the pronoun substitution test is of limited value. The item being replaced may not be a noun. Furthermore nouns can often not be replaced at all depending on their syntactic role. If we have to determine the syntactic role before we do the test there is no point doing it. The reason is that the syntactic role will already tell us how likely an item is to be a noun with the same reliability as the pronoun test. This is because in declarative sentences any item in Subject function will be able to be replaced by a pronoun, whether it's a noun or not. So the chances of the word being replaceable by a pronoun are the same as the chances of the word being a Subject. Neither of these is a guarantee of nounship. The syntactic role that an item has in a given sentence is very rarely a definitive indication of the category of a word. The reason is, of course, that all syntactic roles apart from Predicator may be carried out by more than one type of word or phrase.

A trivial point, a red herring

There are of course some words which sound and are spelt the same. This includes words whose meaning is radically different, as well as words with very similar meanings which belong to different parts of speech. It is common in linguistics to talk about lexemes. We require the notion of a lexeme to indicate that words like liked and liking are versions of the same entity, namely they are inflections of the verb like. So liked and liking are instantiations of the same lexeme.

However, we would not say that man in man of the match and man the decks are instantiations of the same lexeme, even though they may look and sound identical. The reason is that the first is an instance of the noun man whereas the second is an instance of the verb. Because we consider them as instantiations of different lexemes with the same sound and the same spelling, these words are considered homonyms. Although they have some semantic similarities, they represent different types of concept. Also syntactically, the noun man belongs with other instantiations of the noun such as man's, men and men's, whereas the verb belongs with mans, manning, manned and the present tense form man.

So what does this have to do with the question here? Well, it is often said that the category of a word depends on how it used in a sentence. Now if "word" here means a particular series of sounds or a group of letters, then this is trivially, but maybe interestingly, true. We can only understand whether a group of letters represents the noun lexeme man or the verb lexeme man, for example by seeing this group of letters in context.

However, there's another, very harmful and unprincipled idea which sounds very similar, which is that a word should be assigned its part of speech according to what syntactic role, or grammatical function it has in a particular sentence. People who have this kind of idea say things like:

• this word is modifying a noun therefore it is an adjective.

The problem with this type of theory is that it works on the schoolkid assumption that syntactic roles belong to specific word categories. This is because, sadly, the teaching of grammar in schools is of particularly poor quality. Most people are taught at school that words that describe nouns are adjectives, words that describe verbs are adverbs, nouns represent things and verbs represent actions. None of this of course is true.

Here is what Geoffrey Pullum has to say about this problem. The quote is taken from LEXICAL CATEGORIZATION IN ENGLISH DICTIONARIES AND TRADITIONAL GRAMMARS 2009:

Most of the deepest blunders in English grammar as traditionally presented over the past two or three centuries stem from a single long-standing confusion between (i) grammatical categories or word classes; (ii) syntactic functions or grammatical relations; and (iii) semantic and discourse-related notions.

It is surprising to see the tenacity of this confusion. It does not appear in other domains. People do not confuse butter knives with screwdrivers, even though occasionally someone who cannot find a screwdriver may use a butter knife to turn a screw. Yet in grammar people just cannot keep syntactically relevant categories or classes of words separate from the relational properties they have when used in particular constructions, and cannot keep either separate from meaning. They insist on trying to define the first of these in terms of the other two, and they have done so since the very earliest attempts to write grammars of English.

What this means is that we should be able to distinguish between the fact that something modifies a noun and the fact that it is a particular part of speech. Additionally, ideas such as "this word tells us when something happened, so it is an adverb" or even worse "this word tells us when something happened, so it is being used as an adverb" are severely misguided. Neither the semantic content of an item, nor its syntactic role are defining characteristics of its part of speech.

Case Studies

Probably the easiest way to understand how we might run various tests to check the noun status of an item, is to look at these tests in action. There are (or will be shortly) two case studies of particular words in a different post here.

• Comments are not for extended discussion; this conversation has been moved to chat. Please go there to comment: further comments here may be deleted. Feb 25, 2015 at 9:53
• McCawley argues that adjectives modify N-bars, never Ns. This is a very good answer. Dec 31, 2015 at 16:02
• With reference to the note at the start of your post - are you still working on this answer? It looks quite comprehensive already. Mar 15, 2017 at 11:46
• Thanks, @marcinmanhattan ! Good catch! May 21, 2022 at 18:18

A noun generally takes an article ("the"), can be modified by an adjective, cannot be modified by an adverb, cannot take a direct object.

To illustrate, here is a sort of minimal pair between noun and verb: "Eating lobster is forbidden." (This is the first half of the pair.) The subject noun phrase, "eating lobster", has "eating" as its head, so you might suspect that "eating" is a noun. Yet it isn't -- "eating" here is a verb, which you can tell from the fact that it takes the direct object "lobster". Nouns can't have direct objects in English.

In addition, in the example, "eating" cannot be preceded by an article: *"The eating lobster is forbidden" is bad (but note below). If "eating" were a noun, "the"/"a" should be okay.

Also, if "eating" were a noun, it could not be modified by an adverb, yet here, we get "Eating lobster rapidly is forbidden", and if it were a noun, it could be modified by an adjective, but here: *"Rapid eating lobster is forbidden." You can't modify "eating" with the adjective "rapid", because "eating" isn't a noun.

However, if we change the example by removing the direct object, we get the second half of the minimal pair: "The eating of lobster is forbidden." Now, "eating" is a noun. Note the preceding article "the", which is one sign that we're dealing with a noun.

If it's a noun, it ought not to be possible to modify it with an adverb, and it isn't possible: *"The rapidly eating of lobster is forbidden." But it should be possible to modify the noun by an adjective, and it is: "The rapid eating of lobster is forbidden."

Notice that all these methods for distinguishing a noun from a verb are consistent with each other.

Note about the grammaticality of "The eating lobster is forbidden": There may be a grammatical sense of this in which "lobster" is the head noun of the subject and "eating" is a modifier of that noun, but then, of course, "eating" is still not a noun.

• Comments are not for extended discussion; this conversation has been moved to chat. Please go there to comment: further comments here may be deleted. Feb 25, 2015 at 9:52
• Frank's slowly eating his lobster made me feel hungry is grammatical. Are verbs (here, specifically looking at your label for this usage of the ing-form) allowed to be used in genitive constructions in English? I'd say a 'No' answer here is as standard as a 'No' answer to the question 'Are nouns allowed to take direct objects in English?' (And you actually give an unqualified 'Nouns can't have direct objects in English.'). Feb 27, 2015 at 8:36
• "Frank's" in your example might not be genitive. It's the POSS in the POSS-ing complementizer. I don't understand its relation to an ordinary possessive, but it isn't straightforward. Ordinary possessives are definite determiners, but "Frank's" cannot be that -- *"the slowly eating his lobster". Feb 27, 2015 at 14:27
• @GregLee, not to make a chat of this, but have you any further insight into the extraordinary possessive (here, "Frank's")? I ask because of a simple curiosity arising from having been asked to explain the absence of an apostrophe after an edit of "it's" used in this extraordinary possessive sense--and because I found I couldn't readily define or explain the extraordinary possessive sense.
– JEL
Aug 2, 2015 at 17:48
• @GregLee, thank you. When my attempts to explain the edit to "its" from "it's" failed, even in my own estimation, I had to resort to the negative explanation: "the use is not a contraction of 'it is', which would take an apostrophe". Your Frank example exposes a similarly illuminating but largely inexplicable mystery.
– JEL
Aug 3, 2015 at 5:35

One simple feature of a noun is that it can be replaced by "he/she/it" when it is a single noun in singular and by "they" when it is a single noun in plural. I have never tested if this feature really helps in difficult cases, as in English a noun can also be a verb (a cry, to cry), an adjective (the dark, a dark corner) or even an adverb (my home, to go home). Sometimes, I think, the use of the word in a sentence is decisive.

• Comments are not for extended discussion; this conversation has been moved to chat. Please go there to comment: further comments here may be deleted. Feb 25, 2015 at 9:53
• This answer is wrong. It is noun phrases that can be replaced by "he/she/it". Not nouns. Dec 31, 2015 at 15:54
• For me it is basic grammar that a noun can also be a noun phrase. I find it cumbersome to always say "noun or noun phrase". And I wouldn't say the answer is wrong. Peter is my friend/He is my friend. Smoking is unhealthy/It is unhealty.Here we have nouns and not noun phrases. Dec 31, 2015 at 16:42

Case Study: Weekdays

It's probably easiest to get a handle on what some tests for noun status might look like, by seeing one in action. Let's have a look at the item weekdays in a sentence such as:

• It's open weekdays.

The three primary competing word categories for this word are probably adverb, noun and preposition. For want of space, we will just look at the noun and adverb options.

Syntactic function

This phrase is an Adjunct (read adverbial) in the clause structure. It's modifying the verb phrase is open. It's an adjunct because the phrase is not necessary for the sentence to be well formed. The sentence It's open is grammatical without this extra phrase. This syntactic function is associated in school-learned grammar with adverbs. Of course, preposition phrases very often carry out this function too. Just in terms of statistical probability, the fact this is an adjunct makes it statistically more likely to be an adverb than a noun.

However, this phrase is, more specifically, a temporal adjunct. We have seen that noun phrases very often function as temporal adjuncts. Here are some examples:

• It's open the day after tomorrow.
• It's open mornings and afternoons.
• It's open next year.
• It's open three times a week

In accordance with its grammatical relations within this particular sentence, it is perfectly possible, therefore, that weekdays is a noun heading its own Noun Phrase.

Let's look at more data from syntactic functions. If weekdays is a noun, it should be able to function freely as an NP as a Subject, Object or Predicative Complement:

• Weekdays bore me. (Subject)
• I hate weekdays. (Object)
• Monday and Tuesday are weekdays. (Predicative Complement)

If weekdays is an adverb we would expect ungrammatical results when used as a Predicative complement:

• Monday and Tuesday are weekdays.
• *Monday and Tuesday are regularly. (adverb as PC, ungrammatical)

We see above the bad results from the adverb regularly when used as a Predicative complement. In contrast weekdays seems fine.

Lastly in terms of syntactic function, if weekdays is a common noun we would expect it to be able to occur in as Modifier of another noun. If it is an adverb then pre-modification of another noun should be ungrammatical:

• the weekdays association
• a weekdays pass
• *the regularly associations
• *a regularly pass

It we assume that weekdays is a plural noun then we would expect the singular form to be used as a modifier even more freely:

• weekday mornings
• weekday outings
• weekday tickets

The examples above are all grammatical. Compare these with:

• *regularly outings
• *regularly mornings
• *regularly pass

These examples with adverbs, in contrast, are all ungrammatical. This more or less rules out weekdays from being an adverb and provides strong evidence for it being a noun.

Modification

If weekdays is a noun, we expect it to be modifiable by other nouns and by adjectives as well. We do not expect it to be modifiable by adverbs. If it is an adverb we expect it to be modifiable by other adverbs. We don't expect it to be modifiable by adjectives:

• It's open sunny weekdays from 10am to 6pm (adjective)
• It's open regular weekdays from 10am to 6pm (adjective)
• It's open summer weekdays from 10am to 6pm (noun)
• It's open calendar weekdays from 10am to 6pm (noun)
• *It' open very weekdays from 10am to 6pm (adverb)
• *It is open regularly weekdays from 10am to 6pm (adverb)

The examples above show grammatical results for modification by adjectives and nouns and bad result for modification by adverbs. This again shows that weekdays is almost definitely a noun, not an adverb.

Determiners

If weekdays is a noun, we should be able to use it with determiners such as every, some, these, the and so forth. We will save the singular determiner every till we consider whether weekdays is a plural form in the next section. Here are examples with some other determiners:

• It's open some weekdays.
• It's open the weekdays that you mentioned.
• It's open these weekdays, but not those weekdays.
• It's open all weekdays.

Adverbs don't take determiners. The data above constitutes virtually cast iron proof that weekdays is a noun here.

Plural inflections

If weekdays is a noun, it's probably plural given the 'S' ending. We have already seen it in a singular form modifying other nouns further above. When we see it functioning as head of its own NP, it will need a determiner. Below we see it with the determiners every and one:

• It's open every weekday.
• It's open one weekday per month.

This occurrence of weekday with the determiner every is a near cast iron guarantee of nounship. The determiner every only occurs as a dependent in noun phrases headed by nouns.

Genitive inflection

We can find instances of genitively inflected weekday's in examples such as:

• The hours attended on Sunday were the equivalent of a full weekday's schooling.
• We require at least two weekdays' notice to produce this material.

Again adverbs and adverb phrases do not have genitively inflected forms.

Other Morphology

The morphology of weekdays also strongly suggests that it is a noun rather than an adverb. Weekdays lacks the -ly suffix that adverbs in English typically possess. Furthermore it appears to be a compound made from two nouns, week and day(s). Most noun noun compounds in English are nouns. A few also occur as verbs (to railroad someone). Virtually none occur as adverbs.

A complete lack of adverb properties

In addition to the evidence above weekdays shows none of the properties we should expect from adverbs. We have already mentioned that it has non adverb-like morphology and that unlike adverbs weekdays can occur as a predicative complement. In addition weekdays has no comparative forms and does not enter into comparative constructions. It cannot be modified by the kinds of adverbs which we see freely modifying other adverbs:

• so regularly

• so beautifully

• so soon

• *so weekdays

or:

• quite regularly

• quite beautifully

• quite soon

• *quite weekdays

Conclusion.

The word weekdays is a noun, not an adverb.

1. Its internal morphology suggests it is a noun.

2. The phrases it heads can fulfill the syntactic functions that are typical of temporal noun phrases: Subject, Object, Predicative Complement and Adjunct.

3. As with other common nouns, it can function as a modifier in a noun phrase.

4. It can be modified by other nouns and by adjectives.

5. It cannot be modified by adverbs.

6. It has both a singular form and a regular plural form.

7. It has a genitively inflected form.

8. It can occur with a large range of determiners, most importantly with the determiner every.

The strongest evidence here is the fact that it has a plural form and that it can occur with the determiner every. However, all the evidence above clearly demonstrates that weekdays is a noun. It is not a noun with adverb-like properties. It is a bona fide 100% common garden variety noun with no adverb-like properties whatsoever.

• I think "open weekdays" has a prepositional phrase with "(on)" understood. A prepositional phrase has a NP object, which gives us NP as the category of "weekdays". Then "weekdays" can be the noun head of the object of "(on)". There is no conflict in the very same word being a noun in internal composition but the head of the object of a PP adverbial in its external relation to the verb. Mar 1, 2015 at 20:01
• @GregLee I have no deep-rooted objection to that kind of theory (it's just that it's not necessary, so in principle with the proverbial Occam's ...). How would it work with every other weekday? Mar 1, 2015 at 20:04
• With every other weekday? Essentially the same, I suppose. It's a NP in internal structure and the object of an adverbial PP externally. Mar 1, 2015 at 20:28
• is this a trick question? "on" Mar 1, 2015 at 21:02
• Following McCawley, I'd be happy to leave the preposition unspecified, so if there happens to be a real preposition with the right sense, then you can find a paraphrase using it. But if there happens not to be, that's okay, too. Mar 2, 2015 at 13:58

There is no consensus among linguists on how the parts of speech issue is best handled for the trickier cases.

Bas Aarts, in The Handbook of English Linguistics 2006 (ed Aarts & McMahon): English Word Classes and Phrases (Aarts & Haegeman): 2.3 Word class boundaries and gradience gives the analyses of three opposing schools [the extract below is modified].

We could approach ... [the examples given are for ing-form usages] in at least three ways:

Firstly, we could say that verbs and nouns are on a cline or gradient, such that these word classes shade into each other gradually.

Another possibility is to say that [the word in question in its usage in an actual example] is a hybrid element and belongs to the classes [here verb and noun] at the same time. This strategy is adopted in cognitive approaches to grammar. It is also proposed [by] Hudson (2003).

A third possible strategy would be to retain the [traditional/fairytale?] sharp boundaries between the [here] verb and noun categories, and say that though V-ing in sentence A has verbal as well as nominal properties, the verbal ones outweigh the nominal ones.... [And who gets to decide this!?]

Testing for nouns and verbs say is not like doing an A-level chemistry inorganic analysis on a mixture of salts. There, it's indisputable that there is a single correct answer; the single problem the candidates have is to apply the tests correctly. With parts of speech, the periodic table hasn't been agreed upon.

• I must disagree. Or, to use your phrasing, you're wrong. For instance, the strange word 'galore' cannot be said not to be an adjective. It means a flamboyant display etc. But it's a determiner, meaning many. English isn't as well-behaved as macro chemistry. Perhaps one could mention the duality of light here, but I'd argue that that's a different type of implausible beast. // 'All the tests [give consistent results]' is manifestly untrue. 'John's slowly painting the portrait' gives contradictory results. Feb 21, 2015 at 14:53
• This is obscurantism. A chemist might be puzzled by a substance he couldn't classify; I might not understand "galore". What does it show? Some things are hard to figure out. It doesn't mean the nature of things is intrinsically mysterious. And I don't understand your "painting" example -- it's a verb. Feb 21, 2015 at 15:05
• @Edwin. The Oxford Dictionary of English Grammar (p441) in its entry on word classes would agree with you: "There is no single correct way of analysing words into word classes." (Coincidentally or not, one of the co-authors of this reference work is Bas Aarts.)
– Shoe
Feb 22, 2015 at 8:51
• @GregLee: We would like to test words against a fixed number of tests, but who gets to decide what the exact tests are? In the course of history, the list of tests has been changed, refined, criticised, etc. What if some of the tests say galore is a noun, while other tests say it is not? We decide on the tests based on whether they classify the right words as nouns, ones we already think should be nouns. But maybe we change our opinion on some of those words after applying the tests. Etc. This is called the hermeneutic circle, which is perhaps slightly less important in the sciences. Feb 25, 2015 at 2:29
• @Cerberus, I don't know of any official tests or agreed procedures for arriving at a truth of grammar. Or a truth of anything, for that matter. These methodological arguments seem unscientific, to me, and they don't interest me. Feb 25, 2015 at 4:34

I'm English and so a native English speaker, and I consider that in 95+% of cases I can pronounce with certainty both on the grammatical and semantic correctness of an English utterance, although I could not with much certainty identify all of the grammatical terms of the utterance. The answers given here are fascinating and eye-opening when I see that identifying what most English speakers probably think of as the most easily identifiable grammatical term, the noun, as, in a significant(?) number of cases, not so identifiable. And if such is the case for the noun then god help ordinary mortals when it comes to unambiguously identifying other grammatical terms.

It is just recently that I have been looking into the grammar of English because I intend to take a CELTA course, with the intention of teaching English to non-native speakers. As preparation I looked around the web for rules to answer questions about grammar such as is posed initially here, and I found advice on determining a noun by a test of three parts: can the word take "the" or "a"; can it be pluralised; and can it be modified by an adjective. I tried many cases with success until I came upon the sentence "It's at five o'clock.". Having difficulty in identifying the term "five o'clock", I compared this with sentences such as "It's at the races", applied the test to the "the races" and concluded that "the races" is a noun; hence "five o'clock" must be a noun, but it doesn't pass any of the tests. I then tried to find a site that could declare what grammatical term "five o'clock" is, and in Wiktionary it is declared as a noun.

So, if "five o'clock" is a noun then the triple test can't be trusted. Hence, there is no simple test for a noun, and probably for other grammatical terms, as the replies here to the original question indicate. Thus, if I get the CELTA certification and subsequently start to pontificate on the identity of English grammatical terms to non-native English learners (or even to native ones), I can imagine that some of the time I'll be skating on a razor's edge, having to learn to deflect and postpone some questions of English grammar until I can consult more learned sources.

• Five o'clock is etymologically five (strokes) of (the) clock. If dictionaries label o'clock as a noun that is nonsense. This form only occurs after a number giving the time of the clock. You can't say a/the o'clock, a good o'clock, of/to o'clock etc. Such special shortenings of two or three words don't fit into normal word classes. Feb 24, 2015 at 19:56
• Since no one has jumped up and said what the phrase "five o'clock' is I'll try answering it myself. Feb 28, 2015 at 19:04
• (This is a continuation of my preceding comment.) Feb 28, 2015 at 19:05
• (Damn - I'm hitting Enter for a new line but instead the comment is being terminated and added as a finished comment!) Gainsaying Wiktionary, as used in the sentence "It's five o'clock", "five o'clock" is surely acting as an adverb in that it is temporally modifying the verb "is". Feb 28, 2015 at 19:23
• "the races" is a noun phrase (NP), not a noun. Concerning your upcoming skating on thin ice, perhaps you could sometimes say "I don't know" to a question about part of speech, if in fact you don't know. Is that permissible for an English teacher? I often say I don't know -- it's okay for a linguist. Mar 1, 2015 at 12:52