In physics, a reaction in which a particle and its antiparticle (see antimatter) collide and disappear. The annihilation releases energy equal to the original mass m multiplied by the square of the speed of light c, or E = mc2, in accordance with Albert Einstein's special theory of relativity. The energy can appear directly as gamma rays or can convert back to particles and antiparticles (see pair production).

This entry comes from Encyclopædia Britannica Concise.
For the full entry on annihilation, visit

Seen & Heard

What made you look up annihilation? Please tell us what you were reading, watching or discussing that led you here.

Get Our Free Apps
Voice Search, Favorites,
Word of the Day, and More
Join Us on FB & Twitter
Get the Word of the Day and More