Which is botanically a berry: a banana or a strawberry?

Answer

Botanical berries develop from one ovary and have seeds in the flesh. Strawberries are 'accessory fruits' with seeds outside.

Context

Botanists define fruits by how they develop from a flower, not by how they are used in the kitchen. Britannica describes a berry as a simple fleshy fruit, usually with many seeds, that forms from a single ovary of one flower. A banana fits: it develops from one ovary and the fruit wall is fleshy throughout. The seeds in wild bananas are hard and numerous, while the common supermarket types are seedless, with only tiny dark specks where seeds would be. Bananas are usually listed as a modified berry, sometimes with the special name baccate.

The strawberry is a different case. What people eat as the fleshy red part is the enlarged flower base, called the receptacle, not the ovary wall. The true fruits are the small seed-like units on the outside, each a tiny dry achene. Fruit of this kind is called an accessory fruit because a part other than the ovary makes up most of what is eaten. Britannica also classes strawberries with aggregate fruits, formed from many separate ovaries of a single flower, so they are not berries in the strict botanical sense.

The same definition produces other surprises. Tomatoes, grapes and many other fleshy fruits meet the botanical test for a berry, and some citrus fruits and members of the squash family are treated as specialized berry types called hesperidia and pepos. Meanwhile raspberries and blackberries are aggregates of small drupelets, so their common names are misleading. Botanical categories are about structure and development; the culinary word berry is a loose label and often disagrees with it.