testicle vs gonad

testicle and gonad both are nouns.

Word	Noun	Adjective	Verb	Adverb
testicle	Yes	No	No	No
gonad	Yes	No	No	No

As nouns, gonad is a hypernym of testicle; that is, gonad is a word with a broader meaning than testicle:

testicle: one of the two male reproductive glands that produce spermatozoa and secrete androgens
gonad: a gland in which gametes (sex cells) are produced

Other hypernyms of testicle include sex gland, male reproductive gland.

testicle (noun)	gonad (noun)
one of the two male reproductive glands that produce spermatozoa and secrete androgens	a gland in which gametes (sex cells) are produced