penetrate vs fall in

penetrate and fall in both are verbs.

Word	Noun	Adjective	Verb	Adverb
penetrate	No	No	Yes	No
fall in	No	No	Yes	No

As verbs, fall in is a hypernym of penetrate; that is, fall in is a word with a broader meaning than penetrate:

Other hypernyms of penetrate include get together, join.

penetrate (verb)	fall in (verb)
come to understand	break down, literally or metaphorically
become clear or enter one's consciousness or emotions	become part of; become a member of a group or organization
pass into or through, often by overcoming resistance	to take one's place in a military formation or line
insert the penis into the vagina or anus of
spread or diffuse through
make one's way deeper into or through
enter a group or organization in order to spy on the members