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

---

antimatter Scientific  

/ ăn′tĭ-măt′ər /

1. A form of matter that consists of antiparticles.

---

antimatter Cultural  

1. In physics, matter made of antiparticles.

---

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.

Example Sentences

"As a physicist I find it fascinating that a huge question, like why there's matter in the universe instead of antimatter, can be broken down into smaller, step-by-step questions," said Messier.

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

Each particle of matter has an antimatter partner with the same mass but opposite charge, and when they meet, they annihilate into pure energy.

From Science Daily • Dec. 7, 2025

Such simulations could shed light on major open questions in physics, including the imbalance of matter and antimatter, the creation of heavy elements inside supernovae, and the behavior of matter at ultra-high densities.

From Science Daily • Nov. 19, 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