BC that is ad hominem. You ridicule me, not because of my arguments, but because you think you are better qualified than me to speak on these matters.
The complaint in your post: I directed part of the reply to BC because it seemed no-one else was really engaging with the discussion. It’s fine to disagree, but please, others’ “This is what mw.com says, and you don’t know a fucking adjective is” is not really a valid intellectual position. I’ve tried to give a careful explanation of why a noun that modifies a noun remains a noun.
(Quelle surprise, I might add (making a point of getting the French correct if I’m going to be affected enough to use such an expression in the first place.))
Buttercup I am not new to linguistics. I am not using Google in this discussion, except to locate the online dictionaries that have been mentioned. I have the BNC on my desktop because I use it for research almost every day. I have a degree in linguistics with first class honours (yes I know la de da but what do you expect at this point). It must have been different from the one you did, because where I did mine they explained, with reference to Huddlestone’s Grammar of English, how noun modifiers work, and did not tell us fibs about nouns mysteriously transforming themselves into adjectives whenever they modify other nouns: not in the first year or any other year. They gave us the mainstream linguistics view on phrase structure rules and part of speech, and that is what I am repeating here.
I also did a masters and a PhD in computational linguistics, and as part of that experience I learnt a fair amount about how POS is assigned, both by human annotators and automatically. Of course you are right that the structure of the sentence in question is central to the analysis, but at the end of the day, yes, we are concerned precisely with assigning labels. A label is what POS is! We look at the lexicon first (in one kind of computational analysis) to see what POS are available for each word in the sentence, and then choose which is the correct one (for those words that have more than one POS available) based on our parse or analysis of the sentence.
An analogue of this kind of lexicon (probably) exists in the human brain. This is a standard position in psycholinguistics. The lexicon has info about how words are pronounced, what they mean, and what POS they have. It has to know about POS, otherwise we wouldn’t be able to put sentences together systematically when we speak.
Now can you see what a waste of space it would be if every noun, in its lexical entry, had to say “adjective” as well. Waste of space in computer memory and processing, and, presumably, in the mental representation too. Why would the brain hold redundant information? “All nouns can also be adjectives, but only when modifying nouns”.
Also, adjectives behave differently from nominal attributive modifiers. Nearly all adjectives (with a few exceptions like “mere”, and maybe “little”), can also be used predicatively. You can make sentences that have the same underlying syntactic representation: “The big house is over there” is almost the same as “The house is big and it’s over there”. “The book department is over there” cannot be rendered as “*The department is book and it’s over there”.
For “The French teacher” you can’t say “The teacher is French” to mean that the teacher teaches French. “French” can be an adjective or a noun: if “French-adj teacher” is used, it means the teacher has French nationality. If “French-n teacher” is used, it means they teach the subject. You may not be able to hear the difference between French-adj and French-n, but they are two different instantiations of the word, with different parts of speech. That’s how a computer analyses it, and the same applies to your brain.
“This bubblegum music sounds crap” is not the same as “This music is bubblegum and it’s crap”. If you can say the second sentence at all (and I’m not convinced) then the word “bubblegum”, there, is clearly a noun. If that stands, it follows that the attributive modifier “bubblegum” is, indeed, a noun.