boundary

Etymology

bound + -ary, Old French, from Latin.

noun

1. The dividing line or location between two areas.
   City or national boundaries are locations of economic opportunity, especially if the existence of the border is itself the source of a monopoly situation that favors one side over the other (Krakover, 1997). 2017 October, Juin-Jen Chang, Ching-Chong Lai, Ping Wang, “A Tale of Two Cities: Cross-Border Casino Competition Between Detroit and Windsor”, in NBER WORKING PAPER SERIES, archived from the original on 2021-08-15, page 1
2. (figurative, often in the plural) The bounds, confines, or limits between immaterial things (such as one’s comfort zone, privacy, or professional sphere and the realm beyond).
   I didn’t mean to push the boundaries by sending my boss a message on Saturday night.
3. (cricket) An edge or line marking an edge of the playing field.
4. (cricket) An event whereby the ball is struck and either touches or passes over a boundary (with or without bouncing), usually resulting in an award of 4 (four) or 6 (six) runs respectively for the batting team.
5. (topology) (of a set) The set of points in the closure of a set S, not belonging to the interior of that set.