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.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.