Are "many", "few", and "numerous" adjectives or determiners?

Question

So, at first I found some inconsistencies between online dictionaries, with some like Merriam-Webster saying "many" is an adjective, while Wiktionary saying its a determiner. Eventually I had stumbled on to this english.stackexchange question, though I felt like the answer was somewhat vague and inconclusive.

I also realized, when followed by an adjective, there was no comma. For example: "the many brown rabbits" instead of "the many, brown rabbits." This made me lean more towards the determiner side of things, but I did some more digging.

Eventually, I decided to try similar words such as "few" and "numerous". Like the "many" search, Merriam-Webster said it was an adjective while Wiktionary said it was a determiner. This time, Wiktionary did provide me with more information to its interpretation though. The first definition under "determiner" began was "(preceded by another determiner) An indefinite, but usually small, number of." I thought I had found the answer but then I realized, Wiktionary considered "numerous" an adjective, but it had the same comma thing as "many" and "few".

I googled it and the results I got suggested "the numerous brown rabbits" is used in place of "the numerous, brown rabbits."

I'm very confused now, and I would really like to put my mind at ease.

Side notes

First off, I regard Wiktionary and Wikipedia as good references for information. While, the potential for alteration discredits them as a citation, the information itself on non-controversial matters (i.e. not religious or political subjects), is cited to actually credible sources and typically high quality.

Second, this question is not a duplicate of the one I mentioned. That question was asking if "the many" was grammatically correct. The consensus is yes, it is correct to say that. My question is what are these words?

Answer 1

One source of confusion is that there are two possible meanings for the word "determiner":

• Sometimes it is used to refer to a supposed "part of speech": one of several mutually exclusive categories for words such as adjective, verb, noun. (The same word form may correspond to multiple parts of speech, e.g. love can be a noun or a verb, but the noun love and verb love are often analyzed as separate "words". It's hard to say exactly what this means though because the theoretical definition of concepts like "word" is very tricky.)

• Sometimes it is used to refer to a grammatical function: something like predicative complement, adverbial or adnominal. Words or phrases with the same function can have different "parts of speech": for example, in the sentences "The book is green" and "The book is on the table", the adjective green and the prepositional phrase "on the table" both have the function of "predicative complement".

The Cambridge Grammar of the English Language uses the word "determinative" to refer to the part of speech, and "determiner" to refer to the function/grammatical role (see the Q Determiner vs. Determinative). I will follow this convention in the rest of this post. I will use "adjective" to refer to a word class, and "adjectival" to refer to a function (I'm not sure if my use of "adjectival" here is standard, but I don't know the usual terminology).

In the research I did to try to answer a similar question posted on Linguistics SE, ("How to analyze an NP with two determiners?"), I came across the article "Beyond Syntactic Change: various and numerous" by Tine Breban (in Late Modern English Syntax, 2014), which says that Bache (1978) claims that coordination between adnominal modifiers is only possible if they have the same grammatical function.

We can coordinate "many" with adjectives in phrases like "these many and complex causes" or "these many and great dangers", which indicates that it can have an adjectival function.

I don't know if there is any way of determining whether many is a "determinative" that can be used adjectivally in addition to being used as a determiner, or or an adjective that can be used as a determiner in addition to being used adjectivally, or whether we should analyze the two uses as corresponding to two related but distinct words (I think this last kind of approach is unpopular, but there do seem to be some cases where it seems to be necessary to suppose that the same word-form is used for different "words" with distinct parts of speech: -ing-forms perhaps provide the clearest examples of this). The distinction between determinatives and adjectives is given as one possible example of a "slippery" boundary in David Denison's lecture "Parts of speech: Solid citizens or slippery customers?" (2013).

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Related ELU questions:

• One noun but two determiners?

• What part of speech is the word "another"?

Answer 2

Determiners and adjectives are not mutually exclusive. A word can be both, depending on the context.

From Oxford:

many: A large number of.

as determiner ‘many people agreed with her’

as pronoun ‘many think bungee jumping is a new craze’

as adjective ‘one of my many errors’