Doorknob is a noun. It names a thing.
Actually, no. Some people actually collect doorknobs, but doorknobs are mostly used for doors.
DIRECT DOOR HARDWARE doorknobs is easiest to install.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "lecturer" is a noun.