In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy and momentum of the initial pair are conserved in the process and distributed among a set of other particles in the final state. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of such an original pair are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero as long as conservation of energy, conservation of momentum, and conservation of spin are obeyed.

परिशून्यन (Annihilation) किसी वस्तु के सर्वनाश अथवा पूर्णतः समाप्त होने की अवस्था का नाम है। संस्कृतनिष्ट शब्द परिशून्यन का शाब्दिक अर्थ परम रूप से शून्य होना।