|chain (chān) Pronunciation Key
A group of atoms, often of the same element, bound together in a line, branched line, or ring to form a molecule. ◇ In a straight chain, each of the constituent atoms is attached to other single atoms, not to groups of atoms. ◇ In a branched chain, side groups are attached to the chain. ◇ In a closed chain, the atoms are arranged in the shape of a ring.