: 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
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
However, this remarkable biodiversity was nearly destroyed following the introduction of invasive mammals brought by humans – specifically, feral sheep and domestic cats.
—
Scott Travers, Forbes.com, 6 July 2025
The dire wolf disappeared during the Quaternary megafauna extinction, a period when over 178 species of large mammals — known as megafauna — went extinct between 52,000 and 9,000 BCE, long after the Ice Age but before the rise of human civilization.
—Brandi D. Addison, Austin American Statesman, 2 July 2025
The insects use carbon dioxide to locate mammals that invade their nests.
—Gabrielle Chenault, The Tennessean, 2 July 2025
New research has revealed that the Norwegian lemming is one of the youngest mammals on Earth.
—Stephanie Edwards, Discover Magazine, 30 June 2025
See All Example Sentences for mammal
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Scott Travers, Forbes.com, 6 July 2025
The dire wolf disappeared during the Quaternary megafauna extinction, a period when over 178 species of large mammals — known as megafauna — went extinct between 52,000 and 9,000 BCE, long after the Ice Age but before the rise of human civilization.
—Brandi D. Addison, Austin American Statesman, 2 July 2025
The insects use carbon dioxide to locate mammals that invade their nests.
—Gabrielle Chenault, The Tennessean, 2 July 2025
New research has revealed that the Norwegian lemming is one of the youngest mammals on Earth.
—Stephanie Edwards, Discover Magazine, 30 June 2025
See All Example Sentences for mammal
Cite this Entry
“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 10 Jul. 2025.
Copy CitationKids Definition
mammal
noun
mam·mal
ˈmam-əl 
: 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
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