Strange particle

In particle physics, a strange particle is any particle with non-zero strangeness. It must contain at least one strange quark or antiquark. When strange particles were first discovered, beginning with the kaon in the 1940s, they were found to take an unexpectedly long time to decay, and so were given the name strange. Today the large decay time is understood to be due to the presence of the strange quark (or antiquark) which must decay by the relatively slow weak interaction.