1. Symbol S A pale yellow nonmetallic element occurring widely in nature in several free, allotropic and crystal forms and combined in numerous sulfates and sulfides. It is used in black gunpowder, rubber vulcanization, the manufacture of insecticides and pharmaceuticals, and in the preparation of sulfur compounds such as hydrogen sulfide and sulfuric acid. Atomic number 16; atomic weight 32.066; melting point 115.21°C; boiling point 444.61°C; specific gravity at 20°C (rhombic) 2.07, (monoclinic) 2.00; valence 2, 4, 6. See Periodic Table.

2. Any of various butterflies of the subfamily Coliadinae of the family Pieridae, having yellow or orange wings often marked with black.