Substances made of two or more elements chemically bonded together, or enclosed areas with multiple buildings surrounded by walls.
From Old French 'composre' (to put together), from Latin 'componere' (com- + ponere, to place). Used in chemistry since the 17th century; for buildings since the 18th century in colonial contexts.
Table salt is a compound made of sodium and chlorine atoms bonded together—but separately, sodium burns violently in water and chlorine is a poisonous gas, showing how combinations create completely new properties.
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