adjoin

Etymology

From Anglo-Norman adjoindre, from Latin adiungō.

verb

1. (transitive) To be in contact or connection with.
   The living room and dining room adjoin each other.
   We were in the living area, which adjoins the kitchen. 2013, Graeme Simsion, The Rosie Project, page 55
2. (transitive, mathematics, chiefly algebra and number theory) 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).
   textbf Q(√) can be obtained from textbf Q by adjoining √ to textbf Q.