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

Since eliminating red meat, gelatin and other products made from mammal parts, Walsh still has experienced severe reactions.

From The Wall Street Journal ● Jun. 25, 2026

The arrival of a new bull giraffe at a safari park could help save one of the world's rarest species of the mammal.

From BBC ● Jun. 13, 2026

However, the aquatic mammal was already considered ailing and close to death when a final, last-ditch attempt was made earlier in May.

From BBC ● May 31, 2026

But the larger significance is that a longevity mechanism from one mammal was successfully transferred to another.

From Science Daily ● May 10, 2026

The most glaring difference between American and Eurasian food production involved big domestic mammal species.

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

By comparison mule deer, the primary natural prey for wolves in California, appeared in 45% of samples, and small mammals appeared in 51% of samples.

From Los Angeles Times ● Jul. 9, 2026

In a first-of-its-kind study from Australia's Macquarie University, in collaboration with Southern Medical University in China, researchers observed bees showing 'emotion-like behaviours' previously only seen in mammals.

From BBC ● Jul. 9, 2026

The animal, one of the world's most endangered and trafficked mammals, has been stripped of its scales and is being advertised by a Thai account selling "seasonal wild delicacies".

From Barron's ● Jun. 29, 2026

From birds with different beak shapes to mammals that vary in size or color, populations living in different places can often look very different.

From Science Daily ● Jun. 24, 2026

In fact, he wasn’t even going to mention that during his time in South America, 2,500 species of birds and nearly five hundred mammals were collected for the American Museum of Natural History.

From "Death on the River of Doubt" by Samantha Seiple

Related Words

• beast
• creature
• vertebrate