D defs.my
Entry 1 sense Webster, 1913

Boundary

/boun'-dẽr-ē/ · Bound·a·ry · IPA /ˈbaʊndəɹi/
01 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.
pl. Boundaries
  1. 1.
    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.
Syn. 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.