One of a series of organic compounds, being cyclic esters which may be regarded as anhydrides of certain hydroxy acids. In general, they are colorless liquids, having a weak aromatic odor. They are so called because the typical lactone is derived from lactic acid.

a type of cyclic ester

A lactone is a cyclic ester in organic chemistry. It is the condensation product of an alcohol group and a carboxylic acid group in the same molecule. The most stable structure for lactones are the 5-membered lactones (gamma-lactone) and 6-membered lactones (delta-lactone), because of the minimal angle strain in the compounds' structure.