Meaning of “boundary” - Learner’s Dictionary

boundary

noun [ C ] uk us /ˈbaʊndəri/
LINE

a line that divides two areas or forms an edge around an area:

The mountains mark the boundary between the two countries.
LIMIT

a limit:

Such violence is beyond the boundaries of civilized conduct.

(Definition of “boundary” from the Cambridge Learner’s Dictionary © Cambridge University Press)