ˈlakˌtōn noun
( -s )
Etymology: International Scientific Vocabulary lact- + -one
: any of a class of inner esters of hydroxy carboxylic acids formed typically by the loss of a molecule of water from the hydroxyl and carboxyl groups of the acids, characterized by the carbonyl-oxy grouping −OCO− in a ring, and classed according to the position of the hydroxyl group in the parent acid
gamma- lactones from gamma-hydroxy acids contain five-membered rings and delta- lactones from delta-hydroxy acids contain 6-membered rings
— compare sultone
• lac·ton·ic (ˈ)lak|tänik adjective