mortise vs join

mortise and join both are nouns.

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

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

mortise (noun)	join (noun)
a square hole made to receive a tenon and so to form a joint	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

mortise (verb)	join (verb)
join by a tenon and mortise	make contact or come together
cut a hole for a tenon in	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