unionize vs join

unionize is not a noun while join is a noun.

Word	Noun	Adjective	Verb	Adverb
unionize	No	No	Yes	No
join	Yes	No	Yes	No

As verbs, join is a hypernym of unionize; that is, join is a word with a broader meaning than unionize:

Other hypernyms of unionize include fall in, get together.

unionize (noun)	join (noun)
	a set containing all and only the members of two or more given sets
	the shape or manner in which things come together and a connection is made

unionize (verb)	join (verb)
form or join a union	make contact or come together
recruit for a union or organize into a union	cause to become joined or linked
	become part of; become a member of a group or organization
	come into the company of
	be or become joined or united or linked