ligand

noun

1. Biochemistry. a molecule, as an antibody, hormone, or drug, that binds to a receptor.
2. Chemistry. a molecule, ion, or atom that is bonded to the central metal atom of a coordination compound.

noun

1. chem an atom, molecule, radical, or ion forming a complex with a central atom

n.1952, from Latin ligandus, gerundive of ligare “to bind” (see ligament). n.

1. An ion, a molecule, or a molecular group that binds to another chemical entity to form a larger complex.