IPA: /ˈbaʊndəri/
KK: /ˈbaʊndəri/
A line or limit that separates two areas or things, showing where one ends and the other begins.
The fence marks the boundary between the two properties.
Boundary → It is formed from "bound" (from Old French *bond*, meaning a limit or restriction) and "-ary" (meaning relating to or connected with). The word "boundary" refers to something that is related to or connected with a limit or edge.
Think of a 'limit' ('bound') that is 'related to' ('-ary') a specific area — that's what a boundary is.