An amphibian is an animal that can live both in water and on land. The word comes from Greek roots meaning “double life,” which perfectly describes how these creatures exist in two worlds.

Frogs are the most familiar amphibians. They start life as tadpoles swimming in ponds, breathing through gills like fish. Then something remarkable happens: they grow legs, their tails shrink away, and they develop lungs for breathing air. The adult frog can hop around on land but still needs to return to water regularly because its skin must stay moist.

Salamanders and newts are also amphibians, along with the less common caecilians (which look like large worms). Most amphibians lay their soft, jellylike eggs in water, where they hatch into swimming larvae before transforming into their adult forms. This dramatic change is called metamorphosis.

Unlike reptiles, which have dry, scaly skin, amphibians have smooth, moist skin that absorbs water and oxygen. This means they can't venture too far from moisture. You'll rarely find amphibians in deserts, but they thrive near streams, ponds, and in damp forests.

The word is sometimes used more broadly to describe anything that works equally well in two different environments, like amphibious vehicles that can drive on roads and float on water.