https://doi.org/10.1351/goldbook.S06121
Compounds having the structure $\ce{R3S+}$ and associated anion (generally, but not necessarily, all three $\ce{R}$ groups are hydrocarbyl). E.g. $\ce{[(CH3)3S]^{+}Cl^{−}}$, trimethylsulfonium chloride, or 

See: onium compounds