Boundary

Part of speech: noun (n.)

That which indicates or fixes a limit or extent, or marks a bound, as of a territory; a bounding or separating line; a real or imaginary limit. But still his native country lies Beyond the boundaries of the skies. N. Cotton. That bright and tranquil stream, the boundary of Louth and Meath. Macaulay. Sensation and reflection are the boundaries of our thoughts. Locke.

Synonyms: Limit; bound; border; term; termination; barrier; verge; confines; precinct. Bound, Boundary. Boundary, in its original and strictest sense, is a visible object or mark indicating a limit. Bound is the limit itself. But in ordinary usage the two words are made interchangeable.