mammal

noun

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
mə-ˈmā-lē-ən How to pronounce mammal (audio)
ma-
adjective or noun
mammal-like
ˈma-məl-ˌlīk How to pronounce mammal (audio)
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
While transporting large mammals like whales, dolphins and polar bears by plane isn’t unheard of — SeaWorld has been doing it for decades, says Eric Otjen, vice president of zoological operations at the San Diego park. — Lori Weisberg, San Diego Union-Tribune, 22 Aug. 2026 Hibernation on demand Hibernation is a specialty of squirrels, hamsters, and bears, but the neural circuit that triggers it is conserved across mammals, and is present in species that never hibernate in the wild—like mice. — Jacek Krywko, ArsTechnica, 22 Aug. 2026 The small mammal is native to the rainforests of Central and South America. — Amy McDaniel, Fort Worth Star-Telegram, 21 Aug. 2026 The mural includes symbols from the periodic table of elements, and representations of Sir Isaac Newton, scientific equations and evolution — from fish to four-legged mammals to a man carrying a briefcase. — Janice Neumann, Chicago Tribune, 20 Aug. 2026 See All Example Sentences for mammal

Word History

Etymology

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

Rhymes for mammal

See All Rhymes for mammal

Browse Nearby Words

mamma's boy
mammal
mammalian
See all Nearby Words

Cite this Entry

“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 25 Aug. 2026.

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Kids Definition

mammal

noun
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

mammal

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

More from Merriam-Webster on mammal

Nglish: Translation of mammal for Spanish Speakers

Britannica.com: Encyclopedia article about mammal

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