boundary (
http://definr.com/boundary)
n 1: the line or plane indicating the limit or extent of
something [syn:
bound,
bounds]
2: a line determining the limits of an area [syn:
edge,
bound]
3: the greatest possible degree of something: "what he did was
beyond the bounds of acceptable behavior"; "to the limit
of his ability" [syn:
limit,
bounds]