: 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
Shark nets can trap turtles, marine mammals, and even sharks, who are already struggling due to overfishing and climate change.
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Laura Baisas, Popular Science, 24 Sep. 2025
This function is consistent with the developmental origin of crying in the infants’ need for nurturance, and its evolutionary origin in the separation call of juvenile mammals.
—Big Think, 23 Sep. 2025
Its exceptional remains of mammals, birds, and reptiles, 25-15 million years old, help scientists understand Australia’s evolution and its natural history.
—Maria Mocerino, Interesting Engineering, 21 Sep. 2025
However, once human settlers arrived, so did mammals that easily hunted and consumed these ground-dwelling birds.
—Brittney Melton, NPR, 19 Sep. 2025
See All Example Sentences for mammal
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Laura Baisas, Popular Science, 24 Sep. 2025
This function is consistent with the developmental origin of crying in the infants’ need for nurturance, and its evolutionary origin in the separation call of juvenile mammals.
—Big Think, 23 Sep. 2025
Its exceptional remains of mammals, birds, and reptiles, 25-15 million years old, help scientists understand Australia’s evolution and its natural history.
—Maria Mocerino, Interesting Engineering, 21 Sep. 2025
However, once human settlers arrived, so did mammals that easily hunted and consumed these ground-dwelling birds.
—Brittney Melton, NPR, 19 Sep. 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 26 Sep. 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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