Front line and Perimeter

Front line noun - The leading or most important part of a movement.

Perimeter and front line are semantically related. In some cases you can use "Perimeter" instead a noun phrase "Front line".

Perimeter noun - The line or relatively narrow space that marks the outer limit of something.

Front line and perimeter are semantically related. Sometimes you can use "Front line" instead a noun "Perimeter".