Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods, excluding the amniotes. All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems. Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.

நிலநீர் வாழிகள் அல்லது ஈரூடக வாழிகள் எனப்படுபவை நீரிலும் நிலத்திலும் வாழவல்ல முதுகெலும்பி வகையைச் சேர்ந்த விலங்குகள் ஆகும். தவளை, தேரை, குருட்டுபுழு போன்றவை இருவாழ்விகள் ஆகும்.