compound fruit This term was created in the PPO because phenological studies often count aggregate fruits as a single fruit, which is not consistent with the PO definition of fruit. A reproductive structure composed of two or more fruits that have fused during development. Includes aggregate fruits (one flower contains several separate ovaries, which merge during development, e.g., raspberrries) or multiple fruits (several flowers, each with an ovary, develop into small fruits that are clustered or fused together into a larger fruit, e.g., pineapple). simple fruit or compound fruit