: 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
These mammals are found across North America, residing in every kind of habitat from hardwood forests to coastal plains to swamps.
—
Arricca Elin Sansone, Southern Living, 16 Mar. 2026
In fact, nearly three-quarters of mammals are most active at night, as are many insects.
—Stephanie Vermillion, Outside, 16 Mar. 2026
With mammals, wind can determine who hears or smells whom first.
—Sheryl De Vore, Chicago Tribune, 16 Mar. 2026
Newborn mammals find comfort in contact, and rescue animals sometimes seek solace from fuzzy toys in the absence of their families, said Marc Bekoff, professor emeritus of ecology and evolutionary biology at the University of Colorado at Boulder.
—Kyle Melnick The Washington Post, Arkansas Online, 15 Mar. 2026
See All Example Sentences for mammal
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Arricca Elin Sansone, Southern Living, 16 Mar. 2026
In fact, nearly three-quarters of mammals are most active at night, as are many insects.
—Stephanie Vermillion, Outside, 16 Mar. 2026
With mammals, wind can determine who hears or smells whom first.
—Sheryl De Vore, Chicago Tribune, 16 Mar. 2026
Newborn mammals find comfort in contact, and rescue animals sometimes seek solace from fuzzy toys in the absence of their families, said Marc Bekoff, professor emeritus of ecology and evolutionary biology at the University of Colorado at Boulder.
—Kyle Melnick The Washington Post, Arkansas Online, 15 Mar. 2026
See All Example Sentences for mammal
Cite this Entry
“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 18 Mar. 2026.
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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