fall in vs unite

fall in and unite both are verbs.

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

As verbs, unite is a hyponym of fall in; that is, unite is a word with a more specific, narrower meaning than fall in:

fall in (verb)	unite (verb)
break down, literally or metaphorically	become one
become part of; become a member of a group or organization	join or combine
to take one's place in a military formation or line	act in concert or unite in a common purpose or belief
	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