A tadpole is the baby form of a frog or a toad. It hatches from an egg in water and looks nothing like its parents: a round head with a body all in one lump, and a long flat tail for swimming. It has no legs at first. Over some weeks it grows back legs, then front legs, the tail slowly shrinks and gets absorbed into the body, and it becomes a small frog that can climb out of the water. That whole change has a name in biology — metamorphosis — and the tadpole is the most famous example of it after the caterpillar. This is an everyday word, not a scientific one: children learn it very early, and it is the sort of thing people keep in a jar in a primary school classroom in spring. There is one figurative use worth knowing, though it is not common: people occasionally call something tadpole-shaped when it has a big round head and a thin tail, like a comma or a sperm cell in a diagram. Note that the word covers the young of both frogs and toads — English has no separate word for a baby toad.