sulfonium

enUK

sul·fo·ni·um

S0874500 (sŭl-fō′nē-əm)n. A univalent cation containing trivalent sulfur, such as H3S+.
[sulf(o)- + (amm)onium.]

sulfonium

(sʌlˈfəʊnɪəm ) n the US preferred spelling of sulphonium

sul•fo•ni•um

(sʌlˈfoʊ ni əm)

n. the positively charged group H3S + , its salts, or their substitute products. [1890–95; sulf (ur) + -onium]