neighbour vs adjoin

neighbour is a noun but adjoin is not a noun.

Word	Noun	Adjective	Verb	Adverb
neighbour	Yes	No	Yes	No
adjoin	No	No	Yes	No

As verbs, adjoin is a hypernym of neighbour; that is, adjoin is a word with a broader meaning than neighbour:

Other hypernyms of neighbour include abut, border, butt, butt against, butt on, edge, march.

neighbour (noun)	adjoin (noun)
a nearby object of the same kind
a person who lives (or is located) near another

neighbour (verb)	adjoin (verb)
be located near or adjacent to	attach or add
live or be located as a neighbor	lie adjacent to another or share a boundary
	be in direct physical contact with; make contact