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

Examples of mammal in a Sentence

Human beings, dogs, and cats are all mammals.
Recent Examples on the Web Elephants have the longest gestation period among living mammals, lasting 95 weeks on average in the African elephant, according to scientists. Emma Ogao, ABC News, 25 Nov. 2023 Share [Findings] Cetaceans are least likely among mammals to dream profoundly. Rafil Kroll-Zaidi, Harper's Magazine, 22 Nov. 2023 Some officials also worry that the aggressive mammals, which are responsible for about 500 deaths annually in Africa, could be a danger to nearby communities. Margaret Osborne, Smithsonian Magazine, 22 Nov. 2023 Small mammals, like mice, rabbits, and voles, make up the bulk of their diet. Hampton Bourne, Field & Stream, 22 Nov. 2023 But new research, published this summer in Cell Host & Microbe, suggests that long before birth, a similar tactic helps developing humans and other mammals put on a more convincing show. Annie Melchor, Quanta Magazine, 14 Nov. 2023 Elephants are the largest land mammals to roam the planet and some of the most socially intelligent creatures scientists have studied. Sofia Quaglia, Discover Magazine, 30 Oct. 2023 The sanctuary would also protect the ecological qualities of the area including marine mammals, birds, fish, sea turtles, algae and other organisms, as well as rocky reefs, kelp forests and beaches. Summer Lin, Los Angeles Times, 25 Oct. 2023 They are involved in philanthropy and environmentalism Before his death, River was an activist for animal rights and environmental causes, often attending rallies to save marine mammals and preserve the forest. Alex Gurley, Peoplemag, 24 Oct. 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 entry 1

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 2 Dec. 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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