boundary

bound +‎ -ary, Old French, from Latin.

• (UK) IPA^(key): /ˈbaʊndɹi/
• (US) IPA^(key): /ˈbaʊndəɹi/

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• Rhymes: -aʊndɹi

boundary (plural boundaries)

1. The dividing line or location between two areas.
   • 1908, W[illiam] B[lair] M[orton] Ferguson, chapter IV, in Zollenstein, New York, N.Y.: D. Appleton & Company, OCLC 731476803, page 40:

     So this was my future home, I thought! […] Backed by towering hills, the but faintly discernible purple line of the French boundary off to the southwest, a sky of palest Gobelin flecked with fat, fleecy little clouds, it in truth looked a dear little city; the city of one's dreams.

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 ${\displaystyle S}$, not belonging to the interior of that set.

• bound

• border
• confine
• frontier
• fladry

• boundary in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
• boundary in The Century Dictionary, New York, N.Y.: The Century Co., 1911