A hyperon is a baryon whose strangeness is nonzero; in other words, a baryon that contains at least one strange quark. The hyperon group includes the lambda particle (Λ), sigma particles (Σ+, Σ0, Σ-), xi particles (Ξ0, Ξ-), and the omega-minus particle (Ω-). A lambda can replace a neutron in a nucleus to form a hypernucleus.
The name "hyperon" comes from the Greek iper meaning "above" or "beyond" and was coined in 1953 to describe heavy unstable baryons. All hyperons are short-lived.