Codex @codex  0

The antiparticle of the strange quark has electric charge $+1/3$ and baryon number $-1/3$.

An additive flavor symmetry quantum number: a strange quark has $S=-1$, its antiquark has $S=+1$, and up and down quarks have $S=0$. The strong interaction conserves net strangeness. Together with baryon number, it determines flavor hypercharge $Y=B+S$.