frontier

common

The two nations signed a treaty to protect their shared frontier from illegal smuggling.

eastern, northern, etc.

The northern frontier between the two countries has been heavily guarded for decades.

cross

Refugees crossed the frontier illegally to escape the conflict in their country.

control, defend, guard

Soldiers guard the frontier to prevent illegal border crossings.

across the ~

Soldiers were stationed at checkpoints to monitor anyone crossing across the frontier.

along the ~

Small villages dot the landscape along the frontier between the two countries.

at the ~

The customs officers stopped us at the frontier to check our passports.

on the ~

Soldiers patrolled on the frontier to prevent illegal border crossings.

over the ~

Smugglers regularly transport goods over the frontier at night to avoid detection.

~ between

The border patrol officers checked documents at the frontier between the two countries.

~ with

The border dispute occurred along the frontier with Turkey, affecting local communities on both sides.

explore

Early explorers were eager to explore the western frontier in search of new opportunities.

advance, push back

Medical researchers have advanced the frontiers of cancer treatment through their groundbreaking discoveries.