Simple sulfides contain a single sulfide anion (S²⁻), while polysulfides contain chains of two or more sulfur atoms (Sₙ²⁻). Both fall within heading 2830, but polysulfides of metals other than sodium classify under the residual 283090 subheading alongside other non-sodium sulfides.

Natural sulfide minerals and ores (such as pyrite or galena) are classified in the minerals chapters rather than here. Heading 2830 covers chemically defined sulfide and polysulfide compounds, typically produced by synthesis or chemical processing, not raw mineral concentrates.