sulphurous

Sulphurous is an adjective derived from sulfur, the chemical element with the symbol S. In British English, the spelling sulphurous is standard; in American English, sulfurous is common. The term encompasses scientific and figurative uses, referring to sulfur or to sulfur-containing compounds, and to imagery reminiscent of brimstone or hellfire.

In scientific contexts, sulphurous describes sulfur in the lower oxidation states, particularly the +4 state. This includes sulfurous acid (H2SO3) and related species such as sulfites. These sulfurous compounds are typically less oxidizing than their sulfuric ( +6 ) counterparts.

In everyday language, sulphurous is associated with the distinctive odors produced by some sulfur compounds. Elemental sulfur itself is odorless, but when it is converted to sulfur dioxide (SO2) or hydrogen sulfide (H2S) the resulting fumes are pungent, often described as rotten-egg-like or acrid. The term is also widely used metaphorically to evoke brimstone, fire, and infernal imagery, as in sulphurous rhetoric or atmospheres.