Definition
The distance around the outside edge of a circle. It is calculated by multiplying the diameter by pi (approximately 3.1416), or by multiplying the radius by 2 pi.
Plain English
The total length of the curved line that forms a circle — how far you would travel if you walked all the way around it once.
Context Anchor
Seen in basic aircraft math, maintenance drawings, circular parts, wheels, pulleys, and any calculation involving the distance around a round shape.
Derivation
From Latin circumferentia, meaning 'a carrying around,' from circum (around) and ferre (to carry). It literally describes the path carried around a center point.
Why Pilots Care
Propeller tip speed, wheel rotation, and turn radius all depend on circumference. Knowing how to calculate it helps when working with rotational speeds and distances in performance problems.
Intuition Check
Do not confuse circumference with the distance across a circle. Circumference goes around the outside edge; diameter goes straight across through the center.
Example Sentence 1
To find how far the propeller tip travels in one revolution, the mechanic calculated the circumference of the circle traced by the tip.
Example Sentence 2
A circle with a 10-mile radius has a circumference of roughly 62.8 miles.