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.
My brain is a rat’s nest of judicial decisions, fun facts about small mammals, and lots and lots of astronomy stuff. — Sam MacDonald, Scientific American, 28 Oct. 2026 The chattering and barking mammals that scamper through these woodlands rely on the pale fluid to grow fast, providing mammal pups with the raw materials to start turning the soft cartilage of their skeletons to more resilient bone. — Literary Hub, 27 Oct. 2026 Nieder’s leading explanation is that nearly every biological process runs faster in birds than in mammals. — Jacek Krywko, ArsTechnica, 23 Oct. 2026 Federal agencies have overlapping jurisdiction over captive marine mammals –– for sea lions, the USDA oversees their welfare and NOAA decides who can keep them for public display. — Valerie Greene, The Orlando Sentinel, 22 Oct. 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 28 Oct. 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

Britannica.com: Encyclopedia article about mammal

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