sideburn vs facial hair

sideburn and facial hair both are nouns.

Word	Noun	Adjective	Verb	Adverb
sideburn	Yes	No	No	No
facial hair	Yes	No	No	No

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

sideburn: 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)

sideburn (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)