1. Inorganic compounds of sulphur with more electropositive elements. Compounds of sulphur with nonmetals are covalent compounds, e.g. hydrogen sulphide (H₂S). Metals form ionic sulphides containing the S²⁻ ion; these are salts of hydrogen sulphide. Polysulphides can also be produced containing the polymeric ion S_x²⁻.

2. (or thio ethers) Organic compounds that contain the group –S– linked to two hydrocarbon groups. Organic sulphides are named from the linking groups, e.g. dimethyl sulphide (CH₃SCH₃), ethyl methyl sulphide (C₂H₅SCH₃). They are analogues of ethers in which the oxygen is replaced by sulphur (hence the alternative name) but are generally more reactive than ethers. Thus they react with halogen compounds to form sulphonium compounds and can be oxidized to sulphoxides.