mam·​mal ˈma-məl How to pronounce mammal (audio)
: any of a class (Mammalia) of warm-blooded higher vertebrates (such as placentals, marsupials, or monotremes) that nourish their young with milk secreted by mammary glands, have the skin usually more or less covered with hair, and include humans
mammalian adjective or noun
mammal-like adjective
or less commonly mammallike
mammal-like behavior
mammallike reptiles

Example Sentences

Human beings, dogs, and cats are all mammals.
Recent Examples on the Web But Prairie Dog isn’t the only collared mammal that has faced a python. Meghan Bartels, Scientific American, 20 Mar. 2023 There isn't a mammal on the planet that could survive that. Paul Schrodt, Men's Health, 24 Feb. 2023 Caspian seals are the only marine mammal in the Caspian Sea and exist nowhere else in the world. Bryan Pietsch, Washington Post, 5 Dec. 2022 Manatees are Florida’s official state marine mammal but are listed as a threatened species. Curt Anderson, Sun Sentinel, 16 Nov. 2022 The manatee is the official state marine mammal of Alabama. John Sharp |, al, 30 Aug. 2022 Overnight, a shaggy extinct mammal became associated with a buzzy network touted as the independent future of social media. WIRED, 7 Feb. 2023 The male 2,000-pound rhino, Earth's largest land mammal after the elephant, arrived at the park on Sept. 18, 2022, around noon, the report said. Cara Tabachnick, CBS News, 31 Jan. 2023 But the true pulse of the Greater Yellowstone Ecosystem is the hoofbeat of elk, the park’s most abundant large mammal. National Geographic, 12 Jan. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'mammal.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


from base of New Latin Mammalia (Linnaeus), class name, noun derivative from neuter plural of mammālis, from Latin mamma "breast, udder" + -ālis -al entry 1 — more at mamma

First Known Use

1811, in the meaning defined above

Time Traveler
The first known use of mammal was in 1811

Dictionary Entries Near mammal

Cite this Entry

“Mammal.” Dictionary, Merriam-Webster, Accessed 31 Mar. 2023.

Kids Definition


mam·​mal ˈmam-əl How to pronounce mammal (audio)
: any of a class of warm-blooded vertebrates that include human beings and all other animals that nourish their young with milk produced by mammary glands and have the skin usually more or less covered with hair

Medical Definition


mam·​mal ˈmam-əl How to pronounce mammal (audio)
: any of the higher vertebrate animals comprising the class Mammalia
mammalian adjective or noun

More from Merriam-Webster on mammal

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