re·​frac·​tion | \ ri-ˈfrak-shən How to pronounce refraction (audio) \

Definition of refraction

1 : deflection from a straight path undergone by a light ray or energy wave in passing obliquely from one medium (such as air) into another (such as glass) in which its velocity is different
2 : the change in the apparent position of a celestial body due to bending of the light rays emanating from it as they pass through the atmosphere also : the correction to be applied to the apparent position of a body because of this bending
3 : the action of distorting an image by viewing through a medium also : an instance of this

Illustration of refraction

Illustration of refraction

refraction 1: a light ray, b reflected ray, c refracted ray

Keep scrolling for more

Did You Know?

The root of refraction is seen in the notion that the path of a ray of light or wave of energy is "broken" when it is deflected or turned. The effects of refraction can be seen in a rainbow, which is formed when light rays passing into (and reflecting out of) water droplets are bent at different angles depending on their color, so that the light separates into bands of color. The amount of refraction depends on the angle and the type of matter; refraction can occur even when passing through different kinds of air. A mirage, such as you might see in the desert or over a patch of asphalt in the summer, occurs when light passing through warm air meets the very hot air near the surface; reflecting the sky, it often resembles a lake.

Examples of refraction in a Sentence

Recent Examples on the Web

This skid, or refraction, occurs because water is denser than air. Gemma Tarlach, Discover Magazine, "20 Things You Didn't Know About Rainbows," 22 Apr. 2019 Three words: reflection, refraction, and dispersion. Lucia De Stefani, National Geographic, "24 brilliant pictures of rainbows around the world," 15 Mar. 2019 The first demonstration of negative refraction followed within months. Quanta Magazine, "Physicists Close In on ‘Perfect’ Optical Lens," 8 Aug. 2013 Whatever the case, refraction in all its forms is slated to stay—simply choose whichever hue best suits your mood. Calin Van Paris, Vogue, "Olivia Wilde Pulls Off a Straight-from-the-Runway Beauty Look in Paris," 1 Oct. 2018 The Medicare program that provides coverage for millions of Americans age 65 and older doesn’t include routine eye exams, refraction testing or eyeglasses. Michelle Andrews, Washington Post, "Lack Of Insurance Exposes Blind Spots In Vision Care," 15 May 2018 Statements from the American Optometric Association and state organizations say that the technology that an app or computer relies on (known as refraction) doesn’t represent a comprehensive survey. John D. Stoll, WSJ, "Can Health Care Be Disrupted? Warby Parker Offers a Clue," 6 July 2018 The high refraction allows for the possibility of making light-manipulating structures on the surface of the sail that contribute to its reflectivity. John Timmer, Ars Technica, "The material science of building a light sail to take us to Alpha Centauri," 7 May 2018 That generally means that those plans cover a comprehensive eye exam, including refraction, every year, as well as a pair of glasses or contact lenses. Michelle Andrews, Washington Post, "Lack Of Insurance Exposes Blind Spots In Vision Care," 15 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'refraction.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of refraction

1603, in the meaning defined at sense 1

Keep scrolling for more

Learn More about refraction

Statistics for refraction

Last Updated

23 Jun 2019

Look-up Popularity

Time Traveler for refraction

The first known use of refraction was in 1603

See more words from the same year

Keep scrolling for more

More Definitions for refraction


re·​frac·​tion | \ ri-ˈfrak-shən How to pronounce refraction (audio) \

Kids Definition of refraction

: the bending of a ray when it passes at an angle from one medium into another in which its speed is different (as when light passes from air into water)


re·​frac·​tion | \ ri-ˈfrak-shən How to pronounce refraction (audio) \

Medical Definition of refraction

1 : the deflection from a straight path undergone by a light ray or a wave of energy in passing obliquely from one medium (as air) into another (as water or glass) in which its velocity is different
2a : the refractive power of the eye
b : the act or technique of determining ocular refraction and identifying abnormalities as a basis for the prescription of corrective lenses

Keep scrolling for more

More from Merriam-Webster on refraction

Rhyming Dictionary: Words that rhyme with refraction

Spanish Central: Translation of refraction

Nglish: Translation of refraction for Spanish Speakers Encyclopedia article about refraction

Comments on refraction

What made you want to look up refraction? Please tell us where you read or heard it (including the quote, if possible).


showing courage and determination

Get Word of the Day daily email!

Test Your Vocabulary

Words for Summer: A Quiz

  • a closeup of a sunflower
  • Which of the following words means “of or relating to summer”?
Spell It

Can you spell these 10 commonly misspelled words?


Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!