An aggregate fruit is one which develops from
Multicarpellary apocarpous gynoecium
Aggregate fruits or etaerio are those fruits that develop from the merger of multicarpellary apocarpous gynoecium (ovary). In contrast, a simple fruit develops from one ovary. Aggregate fruits may also be called accessory fruits in which parts of the flower other than the ovary become fleshy and form part of the fruit. e.g. raspberry.