Strawberries are not technically berries. They are aggregate fruits because they come from flowers that contain more than one ovary. Berries, on the other hand, come from flowers with a single ovary; berries usually also contain several seeds.
The classification of fruit depends largely on the nature of the ovary. In fleshy fruits, the ovary wall, called the pericarp, is mostly fleshy and can be eaten, although the skin of the fruit may be hard to penetrate. Berries have a single ovary, which is considered a single fruit. The strawberry is not a true berry because it is the result of several ripened ovaries, or fruits, put together. Aggregate fruits such as the strawberry and raspberry are also called syncarps because the individual fruits are small and fused into one.