border vs adjoin

border is a noun but adjoin is not a noun.

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

As verbs, border and adjoin are synonyms defined as:

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

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

Other hypernyms of border include contact, meet, touch.

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

Other hypernyms of border include contact, meet, touch.

border (noun)	adjoin (noun)
a strip forming the outer edge of something
a decorative recessed or relieved surface on an edge
a line that indicates a boundary
the boundary of a surface
the boundary line or the area immediately inside the boundary

border (verb)	adjoin (verb)
lie adjacent to another or share a boundary	attach or add
extend on all sides of simultaneously; encircle	lie adjacent to another or share a boundary
enclose in or as if in a frame	be in direct physical contact with; make contact
provide with a border or edge
form the boundary of; be contiguous to