penetration vs onset

penetration and onset both are nouns.

Word	Noun	Adjective	Verb	Adverb
penetration	Yes	No	No	No
onset	Yes	No	No	No

As nouns, onset is a hypernym of penetration; that is, onset is a word with a broader meaning than penetration:

Other hypernyms of penetration include attack, onrush, onslaught.

penetration (noun)	onset (noun)
an attack that penetrates into enemy territory	(military) an offensive against an enemy (using weapons)
the act of entering into or through something	the beginning or early stages
the act (by a man) of inserting his penis into the vagina of a woman
the depth to which something penetrates (especially the depth reached by a projectile that hits a target)
the ability to make way into or through something
clear or deep perception of a situation