adjoin vs add

adjoin and add both are verbs.

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

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

adjoin: attach or add
add: make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of

adjoin (verb)	add (verb)
attach or add	make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of
lie adjacent to another or share a boundary	make an addition by combining numbers
be in direct physical contact with; make contact	determine the sum of
	state or say further
	bestow a quality on
	constitute an addition