compound noun

[notmyname216]

Why is "knife sharpener" considered a compound noun rather than the combination adjective+noun in this sentence:

I want a knife sharpener.

Thank you in advance.

[Casiopea]

Originally Posted by notmyname216

Why is "knife sharpener" considered a compound noun rather than the combination adjective+noun in this sentence:

I want a knife sharpener.

Thank you in advance.

Well, 'knife' is a thing that cuts. It's a thing, a noun, and a 'sharpener' is a thing that sharpens things. It's also a thing, a noun, so

knife sharpener (noun + noun)

Q: What kind of sharpener?
A: Its' a sharpener (noun) that sharpens knives (noun).
A: *It's a knife one. (Not an adjective)

blue sharpener (adjective + noun)

Q: What kind of sharpener?
A: It's a sharpener (noun) that is blue. (adjective)
A: It's a blue one. (adjective)