fron·tier 
/ˌfrʌnˈtiɚ, Brit ˈfrʌntɪə/ noun
plural fron·tiers /ˌfrʌnˈtiɚ, Brit ˈfrʌntɪə/ noun [count] 1 : a border between two countries
▪ the frontier between Canada and the U.S. 2 : a distant area where few people live
▪ They were sent on an expedition to explore the western frontier. ▪ frontier life 3 : the limits of knowledge in a particular field — usually plural ▪ the frontiers of science ▪ a discovery at the very frontiers of our understanding
▪ the frontier between Canada and the U.S.
▪ They were sent on an expedition to explore the western frontier. ▪ frontier life
