A collective name for any baryon with nonzero strangeness number s. The name hyperon has generally been limited to particles which are semistable, that is, which have long lifetimes relative to 10⁻²² s and which decay by photon emission or through weaker decay interactions. Hyperonic particles which are unstable (that is, with lifetimes shorter than 10⁻²² s) are referred to as excited hyperons. The known hyperons with spin 1/2ℏ (where ℏ is Planck's constant divided by 2π) are Λ, Σ⁻, Σ⁰, and Σ⁺, with s = −1, and Ξ⁻ and Ξ⁰, with s = −2, together with the Ω⁻ particle, which has spin 3/2ℏ and s = −3. The corresponding antihyperons have baryon number B = −1, and opposite values of strangeness s and charge Q; they are all known empirically.