The strange quark is a particle of matter. It is one of the six quarks in the standard model and is considered to be an elementary particle in our current state of knowledge. It is also called the s ( strange) quark.
The strange quark is one of the six quarks, the others being :
The strange quark
Like its companions it is a fermion; it has a fractional electrical charge equal to -1/3 e. It is one of the first three quarks postulated at the beginning of the 1960s independently by Gell-Mann, Yuval Ne'eman and George Zweig to understand and classify the hadrons that were known at the time. The aim was to understand K mesons, also called kaons, discovered in 1947.
Two of the discoverers of quark theory. © universe-review
Currently it is part of what is called the second generation of particles in the standard model.
The existence of the s quark only began to be accepted in the 1960s and especially the beginning of the 1970s when the theory of quark confinement partially explained why quarks were never observed free, but only inside hadrons.
The table of elementary particles in the standard model which includes the strange quark. © MissMJ, Wikipedia