mammal

American  

[mam-uhl] / ˈmæm əl /

noun

• mammals
  plural

1. any vertebrate of the class Mammalia, having the body more or less covered with hair, nourishing the young with milk from the mammary glands, and, with the exception of the egg-laying monotremes, giving birth to live young.

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mammal British  

/ ˈmæməl, mæˈmeɪlɪən /

noun

1. any animal of the Mammalia, a large class of warm-blooded vertebrates having mammary glands in the female, a thoracic diaphragm, and a four-chambered heart. The class includes the whales, carnivores, rodents, bats, primates, etc

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mammal Scientific  

/ măm′əl /

1. Any of various warm-blooded vertebrate animals of the class Mammalia, whose young feed on milk that is produced by the mother's mammary glands. Unlike other vertebrates, mammals have a diaphragm that separates the heart and lungs from the other internal organs, red blood cells that lack a nucleus, and usually hair or fur. All mammals but the monotremes bear live young. Mammals include rodents, cats, dogs, ungulates, cetaceans, and apes.

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Other Word Forms

Derived Forms

• mammal-like
  adjective
• mammalian
  adjective
• mammallike
  adjective

Inflected Forms

Nouns

• mammals
  plural

Etymology

Origin of mammal

First recorded in 1820–30; as singular of New Latin Mammalia, neuter plural of Late Latin mammālis “of the breast”; equivalent to mamma ² + -al ¹

Compare meaning

How does mammal compare to similar and commonly confused words? Explore the most common comparisons:

• marsupial vs. mammal

Explanation

What do you have in common with your hamster, a whale, a bat, a giraffe, and the kid who packs your groceries? Every one is a mammal — a hairy, warm-blooded, milk-drinking vertebrate, just like you. All mammals are part of the scientific class mammalian, which got its name from the mammary glands used to nourish mammal babies. A note of interest: although a characteristic of mammals is that babies are born live, there’s a group of mammals called monotremes, like the platypus, that lay eggs; but whose young’uns, after they hatch, still get fed mama’s milk. Go figure.

Example Sentences

See Examples For:

mammal mammals

In that sense, they can reveal information about lifestyle in much the same way that mammal teeth can reveal information about diet.

From Science Daily ● Aug. 21, 2026

Just this month, New York Governor Kathy Hochul signed the Whale Awareness Act, which requires integrating marine mammal protection efforts and education into state boater safety courses and vessel registration.

From Barron's ● Aug. 18, 2026

The 1972 Marine Mammal Protection Act Muehl admitted to violating prohibits hunting, harassing, capturing, or killing any marine mammal in U.S. waters, or attempting to do so.

From Los Angeles Times ● Aug. 14, 2026

Conservationists say mink have a devastating impact on other wildlife, with the water vole, the UK's fastest-declining mammal, their main targets.

From BBC ● Jul. 6, 2026

If anything, it stood even more upright: at the end of the long chain of adaptive evolution was the well-adjusted, best-erected, most perfected mammal of them all: humans.

From "The Gene" by Siddhartha Mukherjee

Species-rich grasslands offer important habitat for pollinating insects, birds and mammals.

From Science Daily ● Aug. 23, 2026

It was originally used as an osteology and mammals gallery.

From BBC ● Aug. 22, 2026

LoBue now spots the marine mammals basically every time he's out on the water.

From Barron's ● Aug. 18, 2026

The National Park Service has mandated guardrails for the work, including the potential presence of “protected species observers” who would call off drilling if marine mammals are nearby.

From The Wall Street Journal ● Aug. 12, 2026

Big domestic mammals further revolutionized human society by becoming our main means of land transport until the development of railroads in the 19th century.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Related Words

• beast
• creature
• vertebrate