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.

---

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

---

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.

---

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

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

The Etruscan shrew, the smallest mammal, weighs about 1.8 grams.

From Science Daily ● Aug. 9, 2026

"This research underscores the value of long-term marine mammal stranding response programs," said Page.

From Science Daily ● Jul. 21, 2026

But those hypothetical outcomes were foreclosed by mammal extinctions thousands of years earlier.

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

These medium-sized mammals, found only in Africa and Asia, have long, powerful tails, large curved claws, and bodies covered in overlapping scales that resemble a pinecone.

From Science Daily ● Aug. 26, 2026

None of these marine mammals were historically found here as they have been locked out of the coastal waters by ice.

From BBC ● Aug. 20, 2026

"Maternal age effects are incredibly common, from invertebrates up through humans, elephants, other primates and other mammals," said Kristin Gribble, an associate scientist in the Bay Paul Center at the Marine Biological Laboratory.

From Science Daily ● Aug. 19, 2026

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

From Barron's ● Aug. 18, 2026

Like, if you want to see the common characteristics between mammals, reptiles, and fish, for instance, you draw a Venn diagram and list all the attributes of each one inside a circle.

From "Auggie & Me" by R. J. Palacio

Related Words

• beast
• creature
• vertebrate