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antimatter

American  
[an-tee-mat-er, an-tahy-] / ˈæn tiˌmæt ər, ˈæn taɪ- /

noun

Physics.
  1. matter composed only of antiparticles, especially antiprotons, antineutrons, and positrons.


antimatter British  
/ ˈæntɪˌmætə /

noun

  1. a form of matter composed of antiparticles, such as antihydrogen, consisting of antiprotons and positrons

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

antimatter Scientific  
/ ăntĭ-măt′ər /
  1. A form of matter that consists of antiparticles.


antimatter Cultural  

Etymology

Origin of antimatter

First recorded in 1950–55; anti- + matter

Explanation

Antimatter is composed of antiparticles, which have the opposite charge of regular particles. Antimatter is also called negative matter. Matter makes up all the things that exist: everything in the world is matter. Words beginning with anti are opposed to their root. Therefore, antimatter is the opposite of matter. If antimatter and matter were to collide, both would be destroyed, releasing a huge and dangerous amount of energy. This happens because the particles that make up matter and the antiparticles that make up antimatter have opposite electric charges. The existence of antimatter is something studied by physicists.

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Vocabulary lists containing antimatter

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

Looking ahead, experiments involving positronium interference could also make it possible to test how antimatter responds to gravity.

From Science Daily Apr. 28, 2026

In simple terms, neutrinos may not behave exactly like their antimatter counterparts.

From Science Daily Mar. 3, 2026

I think of this book as the antimatter to JD Vance’s “Hillbilly Elegy.”

From The Wall Street Journal Dec. 12, 2025

Instead, almost everything we observe today is made of matter, with almost no antimatter visible in the cosmos.

From Science Daily Dec. 7, 2025

In other words, life would be just the same for the inhabitants of another planet who were both mirror images of us and who were made of antimatter, rather than matter.

From "A Brief History of Time: And Other Essays" by Stephen Hawking

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