sex vs testis

sex and testis both are nouns.

Word	Noun	Adjective	Verb	Adverb
sex	Yes	No	Yes	No
testis	Yes	No	No	No

sex (noun)	testis (noun)
activities associated with sexual intercourse	one of the two male reproductive glands that produce spermatozoa and secrete androgens
the properties that distinguish organisms on the basis of their reproductive roles
all of the feelings resulting from the urge to gratify sexual impulses
either of the two categories (male or female) into which most organisms are divided

sex (verb)	testis (verb)
tell the sex (of young chickens)
to evoke sexual feelings