Amphibians are vertebrate animals that live both in water and on land. Frogs, toads and salamanders are examples of amphibians. Amphibians are able to respire through their skin, and the young of all species of amphibians begin life with gills in the water.
During a process called metamorphosis, amphibians undergo physical changes to develop their adult forms. The adults of some species retain their gills, and many species develop lungs in their adult forms. Another rare order of amphibian is the caecilian, which looks like a worm and is legless, unlike other amphibians. The word "amphibian" comes from Greek root words meaning "dual life," reflecting amphibians' double life in the water and on land in different stages of life.