Adjoin

Adjoin is a verb with several related senses centered on joining, attaching, or bordering. In everyday usage, it describes one object being next to or touching another, or actions that join something to something else. For example, two parcels of land may adjoin, meaning they share a common boundary; a room or building may have adjoining parts that are connected by a shared wall or door. The adjective form adjoining is commonly used to describe things that are next to or attached to each other, such as adjoining rooms.

Etymology and usage notes

The word comes from Old French adjoindre, from Latin ad- “to” and joiner “to join.” It is often used in formal or technical registers, but remains widely understood in general English when describing physical contiguity or connection.

Legal and property contexts

In property law and real estate, adjoin or adjoining is used to describe boundaries and neighboring parcels. For example, a deed may specify that two plots adjoin, indicating they share a boundary line. Adjoining properties may influence zoning, access rights, and survey considerations.

Mathematical and scientific usage

In mathematics and related fields, adjoin denotes enlarging a structure by including a new element. To adjoin an element α to a ring R typically forms the smallest ring containing R and α, denoted R[α]. In field theory, one may adjoin a root of a polynomial to a field, obtaining an extension such as F(a) or F(√2) from F. The concept also appears in algebraic geometry and logic in analogous senses: constructing a larger object that contains certain specified elements.

See also: adjacent, adjacency, adjoining, join.