In particle physics, strangeness (symbol S) is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic interactions which occur in a short period of time. The strangeness of a particle is defined as: S = − − ( n s − − n s ¯ ¯ ) where n s represents the number of strange quarks (s) and n s represents the number of strange antiquarks (s). Evaluation of strangeness production has become an important tool in search, discovery, observation and interpretation of quark–gluon plasma (QGP). Strangeness is an excited state of matter and its decay is governed by CKM mixing.