: 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
Per the study, the female life expectancy advantage is only consistent in mammals, whereas in birds, amphibians and insects, males tend to live longer.
—
Rachel Raposas, PEOPLE, 7 Oct. 2025
The study found that among 528 species of mammals — including humans' closest relative the chimpanzee — females often have the advantage.
—Allison Aubrey, NPR, 6 Oct. 2025
The park’s statement also described the Martin redevelopment as allowing the Seaquarium legacy to continue — albeit one without marine mammals on display.
—Douglas Hanks, Miami Herald, 6 Oct. 2025
Join a morning or evening wildlife tour for the best chance of spotting large mammals like grizzly bears, moose, bull elk, and mountain sheep.
—Lisa Kadane, Travel + Leisure, 6 Oct. 2025
See All Example Sentences for mammal
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Rachel Raposas, PEOPLE, 7 Oct. 2025
The study found that among 528 species of mammals — including humans' closest relative the chimpanzee — females often have the advantage.
—Allison Aubrey, NPR, 6 Oct. 2025
The park’s statement also described the Martin redevelopment as allowing the Seaquarium legacy to continue — albeit one without marine mammals on display.
—Douglas Hanks, Miami Herald, 6 Oct. 2025
Join a morning or evening wildlife tour for the best chance of spotting large mammals like grizzly bears, moose, bull elk, and mountain sheep.
—Lisa Kadane, Travel + Leisure, 6 Oct. 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 13 Oct. 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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