side-whiskers vs facial hair

side-whiskers and facial hair both are nouns.

Word	Noun	Adjective	Verb	Adverb
side-whiskers	Yes	No	No	No
facial hair	Yes	No	No	No

As nouns, facial hair is a hypernym of side-whiskers; that is, facial hair is a word with a broader meaning than side-whiskers:

side-whiskers: facial hair that has grown down the side of a man's face in front of the ears (especially when the rest of the beard is shaved off)
facial hair: hair on the face (especially on the face of a man)

side-whiskers (noun)	facial hair (noun)
facial hair that has grown down the side of a man's face in front of the ears (especially when the rest of the beard is shaved off)	hair on the face (especially on the face of a man)