biceps brachii vs biceps

biceps brachii and biceps both are nouns.

Word	Noun	Adjective	Verb	Adverb
biceps brachii	Yes	No	No	No
biceps	Yes	No	No	No

As nouns, biceps is a hypernym of biceps brachii; that is, biceps is a word with a broader meaning than biceps brachii:

biceps brachii: a muscle that flexes and supinates the forearm
biceps: any skeletal muscle having two origins (but especially the muscle that flexes the forearm)

biceps brachii (noun)	biceps (noun)
a muscle that flexes and supinates the forearm	any skeletal muscle having two origins (but especially the muscle that flexes the forearm)