B

Boundary

noun (plural boundaries)

1. a line which marks the limits of an area; a dividing line: a county boundary the river marks the boundary between the two regions [as modifier]: a boundary wall

(often boundaries) a limit of something abstract, especially a subject or sphere of activity: a community without class or political boundaries

2 .Cricket a hit crossing the limits of the field, scoring four or six runs.

Origin:

early 17th century: variant of dialect bounder, from bound² + -er¹, perhaps on the pattern of limitary

The difference between a boundary and a border has been something I have been discussing.