In general the -ide suffix is used to denote the anion of an element in ionic compounds. For example, oxide refers to the O2- anion in compounds such as iron (III) oxide (Fe2O3) or calcium oxide (CaO). Other anions with the -ide ending include sulfide (S2-) and chloride (Cl-).
Other suffixes are used to denote other types of anions. For example, the -ate suffix usually refers to an oxyanion, an anion formed from an element bonded to oxygen. Therefore, while sulfide is S2-, sulfate is SO42-.