Definition:Perimeter

Definition
The perimeter of a plane figure is the length of its boundary.

Also defined as
By extension, the term perimeter is also frequently used (some would argue erroneously) to mean the boundary itself.

Linguistic Note
The word perimeter derives from the Greek peri (meaning around) and meter (meaning measure).

Hence its literal translation is measure around.

It is pronounced with the emphasis on the second syllable: pe-rim-e-ter.