frontier
[ˈfrʌnˌtiə]
n.
边界, 边境
There have been large-scale military manoeuvres on the frontier.
边境地区曾有过大规模的军事演习。
开发地区的边缘, 边远地区
Areas near the frontier were rough and lawless in the old days.
过去边远地区混乱不堪, 而且没有法律。
尚待开发的领域, 尖端
They are highly interested in the frontiers of science.
他们对于科学的新领域有浓厚的兴趣。