What is a baryon?

A baryon is any particle composed of an odd number of quarks – usually three.

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A baryon is any composite particle that contains an odd number of quarks. A meson is any composite particle that contains an even number of quarks.

There are hundreds of different types of baryon, but most of them are very short-lived. The most common types of baryon in the universe are protons – which consist of two up quarks and one down quark – and neutrons – which consist of one up quark and two down quarks.

The word ‘baryon’ comes from the Greek βαρύς, barýs, meaning ‘heavy’, as many of the baryons have masses greater than those of the more common fundamental particles.