verb

1. To be in contact or connection with.

   “The living room and dining room adjoin each other.”

2. To extend an algebraic object (e.g. a field, a ring etc.) by adding to it (an element not belonging to it) and all finite power series of (the element).

adjective

1. Being in contact at some point or line; joining to

   “an adjoining room”

Synonyms: adjacent, bordering, bordering, contiguous