Adjectives versus Noun Adjuncts [duplicate]

Question

What determines whether something is a "noun adjunct" or just a garden-variety adjective? Does it matter in any meaningful way?

Here is my hypothesis, but I can't find any authoritative source to back it up. I'm hoping someone here can weigh in more definitively.

1. Classification of noun adjuncts is based subjectively on whether the word is in "common usage" as a noun. "Book" and "chicken" are commonly nouns and would be considered noun adjuncts in "book collector" and "chicken soup"; "yellow", not so much.
2. Noun adjuncts may share some common qualities that differentiate them from other adjectives (like not being able to be inflected into superlative forms... one can't be a "book-est collector"). But they are still fundamentally adjectives and may even appear in the dictionary as such if the adjectival usage is common enough.

What I've found so far...

Wikipedia defines a "noun adjunct" as:

an optional noun that modifies another noun; it is a noun functioning as an adjective.

But English words are not decreed to be nouns or adjectives by some higher authority. So it seems strange that one can prescriptively conclude that something "is a noun" in the first place, let alone extrapolate that it "is a noun functioning as an adjective".

The wiki article cites "chicken soup" as an example of a noun adjunct, but at least one dictionary gives a definition for "chicken" as:

adj. (of food) containing, made from, or having the flavor of chicken

So it seems that there are some differing points of view on how to categorize these words.

This question was spawned from some discussion in this question, this question and this other question.

Answer 1

But they are still fundamentally adjectives

Here's where I disagree with the rest of your description, that I otherwise think is correct.

If such a word is "fundamentally" anything (I'll come back to that "if"), it's fundamentally a noun: We think of it as a noun in the abstract. We can't inflect it like like an adjective because it isn't one (though other adjectives may not be able ). They are being used as adjectives, but take them away from that use and their adjectival quality is lost again.

and may even appear in the dictionary as such if the adjectival usage is common enough.

But then it has developed an adjective sense. Or rather, it developed such a sense, and then was recorded as such in the dictionary. Or rather, some lexicographer decided that it had developed such a sense and then recorded it; I'm not convinced the entry you link to was justified; "chicken hot soup" would still be wrong if chicken were accepted as an adjective for the material, but it would be less wrong. I suppose it depends in part in whether we consider "the soup is chicken" to be a contraction of "the soup is chicken soup" or not.

But English words are not decreed to be nouns or adjectives by some higher authority.

So there are no nouns at all?

So it seems strange that one can prescriptively conclude that something "is a noun" in the first place, let alone extrapolate that it "is a noun functioning as an adjective".

Who said anything about prescriptively concluding something "is a noun"?

Now one can prescriptively do so (you can't stop me!) and indeed everyone does; everyone prescriptively decides what they themselves will or will not write. If you decide you are prepared to write "the wall is kitchen" or that you are not, you're being prescriptive.

But we don't need to consider that either. Descriptively you can either observe that people do not generally say "the wall is kitchen" of a kitchen wall, and so it is not an adjective, or you can argue that they might, and so it is an adjective.

I said I'd come back to the "if" of "if such a word is 'fundamentally' anything", and it's because I don't think fundamentally makes sense for things like parts of speech. Parts of speech, especially the traditional parts of speech, are useful classifications. Just how useful is something linguists might debate, as they might also debate just what those parts of speech actually are and e.g. whether determiners are a type of quantifier or separate, and so on.

There are senses in English that can act as a name of a thing or set of things and we call them nouns. They can also be used to modify other nouns they precede, and we call that use noun adjuncts. There are other senses that modify nouns that way and also predicatively and with adverbs further modifying them, and we call them adjectives.

And this is useful up to a point, but I don't think there's anything fundamental about any of it.

There remain qualities that nouns have, even if used as modifiers, that adjectives do not, and therefore the concept of noun and adjective remain usefully separate.

Answer 2

Can the word in question be modified with an enhancer like too or very? Then it's an adjective. Otherwise it's an attributive modifier. (The assumption is we're asking if it's an adjective proper or a noun used attributively.)

In theFreeDictionary an adjective is:

The part of speech that modifies a noun or other substantive by limiting, qualifying, or specifying and distinguished in English morphologically by one of several suffixes, such as -able, -ous, -er, and -est, or syntactically by position directly preceding a noun or nominal phrase.

but generally people understand it as:

a word imputing a characteristic to a noun or pronoun

Grammar-Quizzes.com indicates two descriptions, depending on the audience:

Traditional and ESL (English for Speakers of other Languages) description:

It's a "noun as adjective".

Arguably, in the definition of adjective in the sense of applying a characteristic to a noun or pronoun, a file cabinet uses the noun file to apply a characteristic to another noun (cabinet) and can be considered to be a noun used as an adjective.

Linguistic Description:

Current linguistic analysis describes the examples above as "nouns used as attributive modifiers". That is to say, a "noun" cannot be an "adjective" (a grammatical class) but it can be a "modifier" (a grammatical function). Because it occurs before the head noun, it is called a "pre-head modifier". (Huddleston 4.2.2-3, 5 §14.2)
"Attributive nouns fail to qualify as adjectives by virtue of the grading and adverbial dependents criteria. They don't take very or too or the analytic comparative marker more as modifier." — Nouns as Attributive Modifiers (Huddleston 16.2.4.1)
A fresh cheese cake is delicious.
Both fresh (adj) and cheese (n) function as modifiers to the noun cake. The noun phrase (NP) "A fresh cheese cake" functions as the subject of the clause.

Many common ideas in English are expressed by noun + noun compounds. The first noun is singular and no article is included. The second noun may be plural and may include an article (if it is a count noun) a horse race / some horse races.
The first noun modifies or describes the second noun:
(1) the first noun classifies the second noun: (tells which kind)
milk chocolate (a kind of chocolate) / chocolate milk ( a kind of milk)
a horse race (a kind of race) / a race horse (a kind of horse)
(2) the second noun is the subject of the first noun: ("for")
a shoe shop (a shop that sells shoes; a shop for shoes)
a tooth brush (a brush that cleans teeth; a brush for teeth)
(3) the second noun is a container for the first noun:
a coffee can / cup
a soap dish / box
(4) first noun indicates the material of the second noun:
a gold ring / a silver ring
a paper flower / a silk flower
(Swan 385-6)
Ambiguous pairs occur: a baby doctor (a young doctor, a kind of doctor); a baby store (a store that sells babies, a store for baby goods)

In Linguistic terms, there is no ability to make a noun too noun, very noun, more noun-er, less noun-er, noun-able, or noun-ous, therefore it's never not a noun. The noun can be used attributively but is still considered a noun, even as its function differs from its part of speech.