amphibian

American  

[am-fib-ee-uhn] / æmˈfɪb i ən /

noun

1. any cold-blooded vertebrate of the class Amphibia, comprising frogs and toads, newts and salamanders, and caecilians, the larvae being typically aquatic, breathing by gills, and the adults being typically semiterrestrial, breathing by lungs and through the moist, glandular skin.

2. an amphibious plant.

3. an airplane designed for taking off from and landing on both land and water.

4. Also called amtrac.  a flat-bottomed, armed, military vehicle, equipped with both tracks and a rudder, that can travel either on land or in water, used chiefly for landing assault troops.

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adjective

1. belonging or pertaining to the Amphibia.

2. amphibious.

amphibian British  

/ æmˈfɪbɪən /

noun

1. any cold-blooded vertebrate of the class Amphibia, typically living on land but breeding in water. Their aquatic larvae (tadpoles) undergo metamorphosis into the adult form. The class includes the newts and salamanders, frogs and toads, and caecilians

2. a type of aircraft able to land and take off from both water and land

3. any vehicle able to travel on both water and land

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adjective

1. another word for amphibious

2. of, relating to, or belonging to the class Amphibia

amphibian Scientific  

/ ăm-fĭb′ē-ən /

1. A cold-blooded, smooth-skinned vertebrate of the class Amphibia. Amphibians hatch as aquatic larvae with gills and, in most species, then undergo metamorphosis into four-legged terrestrial adults with lungs for breathing air. The eggs of amphibians are fertilized externally and lack an amnion. Amphibians evolved from lobe-finned fish during the late Devonian Period and include frogs, toads, newts, salamanders, and caecilians.

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Word History

Amphibians, not quite fish and not quite reptiles, were the first vertebrates to live on land. These cold-blooded animals spend their larval stage in water, breathing through their gills. In adulthood they usually live on land, using their lungs to breath air. This double life is also at the root of their name, amphibian, which, like many scientific words, derives from Greek. The Greek prefix amphi– means “both,” or “double,” and the Greek word bios means “life.” Both these elements are widely used in English scientific terminology: bios, for example, is seen in such words as biology, antibiotic, and symbiotic.

Other Word Forms

• nonamphibian adjective

Etymology

Origin of amphibian

1630–40; < Latin amphibi ( a ), neuter plural of amphibius (adj.) ( amphibious ) + -an

Explanation

An amphibian is a cold-blooded vertebrate animal that is born in water and breathes with gills. As the larva grows into its adult form, the animal's lungs develop the ability to breathe air, and the animal can live on land. Frogs, toads, and salamanders are all amphibians. The word amphibian comes from the Greek word amphibios, which means "to live a double life." The noun amphibian has its roots in the words amphi, meaning "of both kinds," and bios, meaning "life." The word is used for the class of animals that spend part of their lives in water and part on land. The word can also be used as an adjective to describe the animals that live this way. You might be interested to know that the largest amphibian weighs about 140 pounds and the smallest weighs only a few grams.

Example Sentences

Worldwide, scientists have identified more than 9,000 amphibian species, and about 100 to 200 new ones are added each year, he said.

From Science Daily • Mar. 9, 2026

Those meals came from 18 humans, one amphibian, six birds, one canid, and one mouse.

From Science Daily • Jan. 15, 2026

But the relative lack of rain this spring and summer could lead to lower insect and amphibian numbers next year since eggs may not be laid and wetland areas are drying up.

From BBC • Jul. 25, 2025

Among these is the wood frog, a Canadian amphibian that freezes solid for eight months of the year.

From Salon • Apr. 20, 2025

My heart, that amphibian, moving that moment between two elements: one, excitement; the other, fear.

From "Middlesex: A Novel" by Jeffrey Eugenides

Related Words

• frog
• salamander
• toad