unite vs fall in

unite and fall in both are verbs.

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

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

Other hypernyms of unite include get together, join.

unite (verb)	fall in (verb)
become one	break down, literally or metaphorically
join or combine	become part of; become a member of a group or organization
act in concert or unite in a common purpose or belief	to take one's place in a military formation or line
bring together for a common purpose or action or ideology or in a shared situation
have or possess in combination
be or become joined or united or linked