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 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
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.
Swimmer's itch is a skin rash caused by an allergic reaction to microscopic parasites that infect some birds and mammals, according to the Centers for Disease Control and Prevention. Jalen Williams, Freep.com, 11 July 2025 Lefebvre has been studying harmful algae blooms for her entire career and was involved in the first-ever study in 1998 that found domoic acid was impacting marine mammals in Central California. Julia Jacobo, ABC News, 9 July 2025 Nictitating membranes act as a type of third eyelid going horizontally across the eye and found in some animals like birds, reptiles and some mammals. Irene Wright july 8, Miami Herald, 8 July 2025 The city is home to 1,600 species of plants, 5,200 insects, around 100 birds, 40 mammals, and 30 reptile and amphibian species. Krista Langlois, Smithsonian Magazine, 7 July 2025 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

Browse Nearby Words

Cite this Entry

“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 21 Jul. 2025.

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 adjective or noun

More from Merriam-Webster on mammal

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