# What is the correct name for AlS_3?

Aluminum sulfide ($A {l}_{2} {S}_{3}$)
As far as I know, $A l {S}_{3}$ is not a real compound, so I'll use $A {l}_{2} {S}_{3}$ which may be what your question is asking for..
Since this is a binary ionic compound, the name consists of the cation ($A l$) followed by the anion ($S$) with a suffixe of -ide, so the name of $A {l}_{2} {S}_{3}$ is aluminum sulfide.