frontier

Armed guards patrol the mountain frontier to prevent illegal crossings between the two countries.

(Chinese) 武装警卫在山地边境巡逻，以防止两国之间的非法越境。

Early American settlers faced many hardships as they moved west toward the wild frontier.

(Chinese) 早期美国定居者在向西部荒野边境迁移的过程中面临着许多艰辛。