Frontier
01
边疆, 边界
the outer edge of occupied or developed land, beyond which lies unsettled territory
例子
Pioneers migrated westward, steadily pushing the frontier of settlement into new territories.
先驱者们向西迁移，不断将定居的边界推向新的领土。
During the 19th century, settlers pushed west across the Great Plains, gradually expanding the frontier of the young American nation.
在19世纪，定居者向西推进穿过大平原，逐渐扩大了年轻的美国国家的边疆。
02
前沿, 新领域
an undeveloped field of study; a topic inviting research and development
03
边界, 边疆
an area located at a border, where two countries or regions meet
例子
The town lies right on the frontier, making it a strategic location for trade.
该镇位于边境上，使其成为贸易的战略要地。
Customs officers work diligently at the frontier to enforce immigration laws.
海关官员在边境辛勤工作，以执行移民法。
