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• arc
  arc

  noun

  any unbroken part of the circumference of a circle or other curved line.
• ARC
  ARC

  noun

  AIDS-related complex.

arc

¹ American  

[ahrk] / ɑrk /

noun

arcs plural

1. Geometry. any unbroken part of the circumference of a circle or other curved line.

2. Also called electric arc.  Electricity. a luminous bridge formed in a gap between two electrodes.

3. Astronomy. the part of a circle representing the apparent course of a heavenly body.

4. anything bow-shaped.

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verb (used without object)

arced, arcked, arcing, arcking

1. to form an electric arc.

2. to move in a curve suggestive of an arc.

ARC ² American  

[ahrk] / ɑrk /

noun

1. Pathology. AIDS-related complex.

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ARC ³ American  

Or A.R.C.

abbreviation

1. American Red Cross.

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arc ¹ British  

/ ɑːk /

noun

1. something curved in shape

2. part of an unbroken curved line

3. a luminous discharge that occurs when an electric current flows between two electrodes or any other two surfaces separated by a small gap and a high potential difference

4. astronomy a circular section of the apparent path of a celestial body

5. maths a section of a curve, graph, or geometric figure

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verb

1. (intr) to form an arc

prefix

1. maths specifying an inverse trigonometric function: usually written arcsin , arctan , arcsec , etc, or sometimes sin–1 , tan–1 , sec–1 , etc

ARC ² British  

abbreviation

1. AIDS-related complex: an early condition in which a person infected with the AIDS virus may suffer from such mild symptoms as loss of weight, fever, etc

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arc Scientific  

/ ärk /

1. A segment of a circle.

2. See electric arc

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Other Word Forms

Noun Inflected Forms

• arcs
  plural

Etymology

Origin of arc

1350–1400; Middle English ark < Latin arcus bow, arch, curve

Explanation

An arc is a curve. You can describe the bend of a rainbow as an arc. In math, an arc is one section of a circle, but in life you can use the word to mean any curved shape, like the arc of a ballerina's arm or the graceful arc of a flowering vine over a trellis. In the 14th century, arc first meant the movement of the sun in the sky, from the Old French arc, "bow or arch," and the Latin root arcus, also "bow or arch."

Example Sentences

I’m sipping coffee out of my “embarrassing” Starbucks mug as I write this and thinking about the climb up the Arc de Triomphe with my daughter on her first visit last year.

From The Wall Street Journal • Jul. 1, 2026

In a study of mice, they found that a brain protein called Arc, which normally helps neurons communicate, also appears to help toxic Tau spread from diseased brain cells to healthy ones.

From Science Daily • Jun. 30, 2026

In mice without Arc, toxic Tau remained trapped inside neurons, causing those already sick cells to die more quickly.

From Science Daily • Jun. 30, 2026

“I didn’t hold some big press conference and hop up on a white horse and declare myself Joan of Arc and the savior of all things Los Angeles,” she said.

From Los Angeles Times • Jun. 5, 2026

Not wanting to be left out, I fired Leopardon’s Arc Turn weapon, a gold boomerang that launched from the mech’s forehead.

From "Ready Player One: A Novel" by Ernest Cline

Related Words

• arch