Symbol s. A property of certain hadrons (K-mesons and hyperons) that decay more slowly than would have been expected from the large amount of energy released in the process. These particles were assigned the quantum number s to account for this behaviour. For nucleons and other nonstrange particles s=0; for strange particles s does not equal zero but has an integral value. In quark theory (see elementary particles), hadrons with the property of strangeness contain a strange quark or its antiquark.