circumference

noun

cir·​cum·​fer·​ence sər-ˈkəm(p)-f(ə-)rən(t)s 

sə-, 

-fərn(t)s

1

: the perimeter of a circle

The circle measures 22 inches in circumference.

2

: the external boundary or surface of a figure or object : periphery

from the center to the circumference of the sphere

circumferential

sər-ˌkəm(p)-fə-ˈren(t)-shəl 

sə-

adjective

Did you know?

Attempts have been made to measure the circumference of the earth since the time of Aristotle. The calculation that Columbus was relying on led him to think he could reach China by sailing west more quickly than by sailing east. But that measurement had calculated the earth's circumference as about a quarter too small, and the rest is history. Columbus wasn't the only one who got it wrong; many later attempts continued to produce different measurements for the earth's circumference—even though the Greeks had calculated it correctly way back in the 3rd century B.C.

Synonyms of circumference

• diameter
• radius
• equator

Examples of circumference in a Sentence

What is the circumference of the Earth at the equator?

The circle is 38 inches in circumference.

The fence marks the circumference of the field.

Recent Examples on the Web

Body measurements for height, waist, hips and Relative Fat Mass, an index that estimates body fat percentage from height, waist circumference and gender, have remained stable. — Rosemary Feitelberg, Footwear News, 24 June 2026

That eight-step process analyses balls according to eight criteria, including circumference, water absorption, rebound height, shape and size retention, and sphericity (a measurement of roundness). — Liam Tharme, New York Times, 20 June 2026

Famous for its enormous trunk -- about 36 feet in circumference -- and gnarled branches, the Major Oak was believed to be about 1,200 years old, according to the RSPB Bird & Wildlife Conservation Charity. — ABC News, 19 June 2026

The most astonishing thing about this is that these numbers appear in the simplest contexts, such as when calculating the circumference of a circle or the diagonal of a square. — Manon Bischoff, Scientific American, 19 June 2026

Word History

Etymology

Middle English, from Middle French & Latin; Middle French, from Latin circumferentia, from circumferre to carry around, from circum- + ferre to carry — more at bear

First Known Use

14th century, in the meaning defined at sense 1

Kids Definition

circumference

noun

cir·​cum·​fer·​ence sə(r)-ˈkəm(p)-fərn(t)s 

-f(ə-)rən(t)s

1

: a line that goes around or encloses a circle

2

: the outer boundary of a figure or area

3

: the distance around something

the circumference of the earth at the equator