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Synonyms

mammal

American  
[mam-uhl] / ˈmæm əl /

noun

  1. any vertebrate of the class Mammalia, having the body more or less covered with hair, nourishing the young with milk from the mammary glands, and, with the exception of the egg-laying monotremes, giving birth to live young.

mammal British  
/ ˈmæməl, mæˈmeɪlɪən /

noun

  1. any animal of the Mammalia, a large class of warm-blooded vertebrates having mammary glands in the female, a thoracic diaphragm, and a four-chambered heart. The class includes the whales, carnivores, rodents, bats, primates, etc

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
mammal Scientific  
/ măm′əl /

  1. Any of various warm-blooded vertebrate animals of the class Mammalia, whose young feed on milk that is produced by the mother's mammary glands. Unlike other vertebrates, mammals have a diaphragm that separates the heart and lungs from the other internal organs, red blood cells that lack a nucleus, and usually hair or fur. All mammals but the monotremes bear live young. Mammals include rodents, cats, dogs, ungulates, cetaceans, and apes.

Other Word Forms

  • mammal-like adjective
  • mammalian adjective
  • mammallike adjective

Etymology

Origin of mammal

First recorded in 1820–30; as singular of New Latin Mammalia, neuter plural of Late Latin mammālis “of the breast”; equivalent to mamma 2 + -al 1

Compare meaning

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The marine mammal, which is stuck on a sandbank, was first spotted in Lübeck Bay on Monday.

From BBC • Mar. 26, 2026

It’s not exactly a chicken and dinosaur-egg question, but which came first, the mammal or the giant lizard?

From The Wall Street Journal • Feb. 10, 2026

One of the defining breakthroughs in mammal evolution was the rise of highly sensitive hearing.

From Science Daily • Jan. 19, 2026

By Christmas, the enormous mammal had done serious damage — turning on a gas line under the house —that forced Johnson to live without hot water.

From Los Angeles Times • Jan. 9, 2026

Eurasia has the largest number of big terrestrial wild mammal species, whether or not ancestral to a domesticated species.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.