sex vs secern

sex is a noun but secern is not a noun.

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

As verbs, secern is a hypernym of sex; that is, secern is a word with a broader meaning than sex:

sex (noun)	secern (noun)
activities associated with sexual intercourse
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)	secern (verb)
tell the sex (of young chickens)	mark as different
to evoke sexual feelings