circumference

American  

[ser-kuhm-fer-uhns] / sərˈkʌm fər əns /

noun

1. the outer boundary, especially of a circular area; perimeter.

   the circumference of a circle.

   Synonyms:

   circuit, periphery

2. the length of such a boundary.

   a one-mile circumference.

3. the area within a bounding line.

   the vast circumference of his mind.

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circumference British  

/ səˌkʌmfəˈrɛnʃəl, səˈkʌmfərəns /

noun

1. the boundary of a specific area or geometric figure, esp of a circle

2. the length of a closed geometric curve, esp of a circle. The circumference of a circle is equal to the diameter multiplied by π

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circumference Scientific  

/ sər-kŭm′fər-əns /

1. The boundary line of a circle.

2. The boundary line of a figure, area, or object.

3. The length of such a boundary. The circumference of a circle is computed by multiplying the diameter by pi.

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circumference Cultural  

1. The measure of the distance around a circle.

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Other Word Forms

• circumferential adjective
• circumferentially adverb

Etymology

Origin of circumference

1350–1400; Middle English < Late Latin circumferentia, equivalent to circum- circum- + fer- (stem of ferre to carry) + -entia -ence

Explanation

The distance around a circle is called the circumference, and although circumference is often used when talking about round things, it can mean a boundary of any shape that completely surrounds something. It’s no coincidence that the first part of circumference looks like circle. The Latin word circum means “around,” and the root ferre is the Latin verb for “carry,” so imagine carrying a puppy around a circle pit of lava: the path you walk is the circumference. If you want to buy a new hat, you’ll need to measure the circumference of your head, and patrolling the circumference of your castle is a good way to protect against dragons.

Example Sentences

In a phase 2 trial in Chinese patients with Type 2 diabetes, UBT251 also showed a mean blood sugar reduction of up to 2.16% while improving patient’s waist circumference and blood pressure.

From The Wall Street Journal • Mar. 25, 2026

UBT251 led to a mean weight loss of 19.7% after 24 weeks of treatment and also improved patients’ waist circumference, blood glucose, blood pressure, and lipids relative to placebo, the companies said.

From Barron's • Feb. 24, 2026

The team has previously developed a therapy aimed at reducing waist circumference and plans to evaluate how different treatment strategies might benefit this newly defined group.

From Science Daily • Dec. 31, 2025

But the sheer sort of circumference of the dress makes her a woman who comes into a room and takes up space.

From Los Angeles Times • Dec. 16, 2025

With them he deduced the circumference of the Earth with an error of only a few percent, a remarkable achievement for 2,200 years ago.

From "Cosmos" by Carl Sagan

Related Words

• girth