flexor vs flexor muscle

flexor and flexor muscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
flexor	Yes	No	No	No
flexor muscle	Yes	No	No	No

As nouns, flexor and flexor muscle are synonyms defined as:

flexor and flexor muscle: a skeletal muscle whose contraction bends a joint

flexor (noun)	flexor muscle (noun)
a skeletal muscle whose contraction bends a joint	a skeletal muscle whose contraction bends a joint