What does perimeter mean?
A perimeter is the outer boundary of an area, object, or geometric figure. In everyday use, it often describes a line or zone around a place, especially one marked by a fence, wall, checkpoint, or other barrier. In geometry, the perimeter is the total distance around a two-dimensional shape, whereas its area is the space enclosed by that boundary. The term also has figurative uses: “the perimeter of the debate” means the outer limits of the issue or the positions people can reasonably consider. Perimeter is especially associated with security, military activity, surveying, construction, and mathematics, but it remains a general word for any clearly defined outer limit. Its useful distinction is that it usually implies an edge enclosing a space rather than simply a point on a surface. Unlike “circumference,” which is especially associated with circles and the measurement around them, “perimeter” applies broadly to any closed shape or bounded area.
The enclosing outer boundary of an area, object, or geometric figure; by extension, the outer limits of a place, institution, or field of activity.
"The shape has a perimeter of 24 centimetres."
As a countable noun, it may refer either to the boundary line itself or, in geometry, to the total distance around a closed figure.
To form or mark the enclosing boundary of something, especially by means of a fence, wall, or other barrier.
"The old railway line was perimetered by a steel barrier."
The verb is formal and relatively uncommon outside specialized contexts.
“Perimeters” is the standard plural of the noun, used for the boundaries of multiple areas, objects, or figures.
"The two properties share separate perimeters."
The word combines the Greek roots for “around” and “boundary,” making perimeter literally the boundary around.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does perimeter come from?
The word entered English through French périmètre, from Latin perimetrum, based on Greek perimoros, “having a circumference.” Greek perimoros combines the prefix peri-, meaning “around,” with horos, meaning “boundary.” The related boundary root horos also gave English the word horizon, while the measuring sense developed in forms such as perimetry and perimetric.
Related word forms
How perimeter is actually used
As a noun, perimeter is common in formal, technical, and journalistic writing, especially for physical boundaries and geometric measurement. As a verb, it is formal and much less common; perimetering usually means enclosing something with a barrier or defining its outer edge. The word is used in both British and American English without a significant regional difference.
Easily confused with perimeter
A perimeter is the boundary itself, whereas a circumference is the distance measured around a closed curve or circular object.
Perimeter usually means a definite enclosing boundary, while periphery often refers more generally to an outer region or the less central parts of a place or subject.