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boundary

/ˈbaʊndəri//ˈbaʊndəri/·noun
a line that marks the limit or edge of an area or a domain
Fig. 1 — A single line runs down the middle of the floor, and on either side of it the small shapes drift about as they please.
01Definition

A boundary is where one thing ends and another begins — a line, real or agreed, that separates inside from outside, mine from yours, one field of study from the next. Physical boundaries fence off land; personal boundaries mark what you will and won't accept; disciplinary boundaries divide subjects. The word stresses the dividing edge itself rather than the space it encloses, which is why we speak of 'pushing the boundaries' — moving the very line that decides how far is too far.

02In use
  • iThe river forms a natural boundary between the two countries.
  • iiEvery academic boundary is a kind of constraint, useful until a new question refuses to respect it.
  • iiiCrossing that boundary felt like stepping over a threshold there was no coming back from.
03Collocations
  • push the boundaries
  • cross a boundary
  • a clear boundary
  • set boundaries
  • the boundary between

Family bound (verb) · boundless (adjective) · bounded (adjective)

04Relations

=border, limit, edge, perimeter, demarcation

≠centre, interior

06TOEFL & IELTS

A flexible academic noun. Literally it means a border (IELTS maps, geography); figuratively it means a limit (TOEFL lectures on ethics, science, psychology). 'Push the boundaries of' is a strong collocation for essays on progress and innovation. Mind the spelling — bound-a-ry — and the plural boundaries. Distinguish it from 'border' (usually political or physical) when the sense is abstract limits.

07Asked
What is the difference between a boundary and a border?
A border is the political, enforced kind of edge — countries, checkpoints, passports. A boundary is any dividing line at all: a property line, the edge of a science, what you will and won't accept. Every border is a boundary; almost no boundary is a border. When the edge is abstract, boundary is the only one of the two that fits.
What does 'push the boundaries' mean?
To go beyond what is currently accepted or thought possible — 'the film pushes the boundaries of animation'. The image is exact: the boundary is the agreed line of the permissible, and pushing it moves the line itself rather than breaking through it. Its more colloquial cousin is 'push the envelope', from test-flight jargon.
What are personal boundaries?
In psychology's vocabulary, the limits a person sets on what behaviour they will accept — on their time, body, feelings and attention. 'Setting a boundary' is stating such a limit out loud. The scene above is the mechanism in miniature: the line is invisible until something presses against it, and then it is the firmest thing in the room.
What is the difference between a boundary and a limit?
A limit is a maximum — how far, how much, how fast, a point on a scale. A boundary is an edge between two territories — inside and outside, yours and mine. You reach a limit; you cross a boundary. Speed has limits; countries and disciplines have boundaries.
How do you spell boundary?
B-o-u-n-d-a-r-y — three syllables with an a that speech often swallows, which is why 'boundry' is the classic misspelling. The plural is boundaries. Anchor the a with the word's cousin bound: out of bounds, bounded by hedges.
Is 'bound' related to boundary?
Yes — bound is the working verb and adjective of the family: a field bounded by hedges, 'out of bounds' in sport, boundless meaning without limits at all. Mathematics leans on the same stem ('bounded above'). Boundary is simply the noun that names the line the others keep pointing at.