demarcation

noun

1. (countable, uncountable)The act of marking off a boundary or setting a limit, notably by belligerents signing a treaty or ceasefire.
2. (countable, uncountable)A limit thus fixed, in full demarcation line.

   “About sunset, he was leaning on the remains of an old wall, which had once probably surrounded a Roman encampment, and now served as a line of demarcation between two villages, as jealous of each other's claims as near neighbours usually are.”

3. (countable, uncountable)Any strictly defined separation.

   “There is an alleged, in fact somewhat artificial demarcation in the type of work done by members of different trade unions.”

   “In the sea there is no demarcation between the hunter and the hunted, as there is on the African plains.”

   “Certainly no clear line of demarcation has as yet been drawn between species and sub-species—that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences. These differences blend into each other in an insensible series; and a series impresses the mind with the idea of an actual passage.”