Amphibious means able to live or operate both on land and in water. Frogs are amphibious animals: they start life as tadpoles swimming in ponds, then grow legs and lungs that let them hop around on shore while still being excellent swimmers. Salamanders, newts, and toads are amphibious too.

Think about how different swimming and walking are: one requires gills or holding your breath, the other requires legs and lungs. Amphibious creatures handle both.

The military uses amphibious to describe vehicles and operations that work on both land and water. An amphibious vehicle might drive down a road like a truck, then drive straight into a river and motor across like a boat. During World War II, amphibious landings involved troops traveling by ship, then storming onto beaches to fight on land. The famous D-Day invasion was an amphibious operation, with soldiers crossing the English Channel before landing in France.

When something is truly amphibious, it doesn't just survive in both environments: it can thrive in them. That's what makes the word more interesting than simply saying “can go on land and water.”