ETYM Latin circumferentia.
In geometry, the curved line that encloses a curved plane figure, for example a circle or an ellipse. Its length varies according to the nature of the curve, and may be ascertained by the appropriate formula. The circumference of a circle is pd or 2pr, where d is the diameter of the circle, r is its radius, and p is the constant pi, approximately equal to 3.1416.
1. The length of the closed curve of a circle.
2. The size of something as given by the distance around it; SYN. perimeter.
ETYM Greek; peri around + metron measure: cf. French périmčtre.
Outer boundary, and its length.
Or boundary; Line drawn around the edge of an area or shape. For example, the perimeter of a rectangle is the sum of its four sides; the perimeter of a circle is known as its circumference.
A line enclosing a plane areas.