A lactone is a cyclic ester in chemistry. It is the condensation product of an alcohol group and a carboxylic acid group in the same molecule. Prefixes may indicate the ring size: beta-lactone (4-membered), gamma-lactone (5-membered), delta-lactone (6-membered ring).
Examples
gamma-Butyrolactone (GBL):
D-Glucono-delta-lactone (E575):
See also