What does mammal mean?
A mammal is a warm-blooded vertebrate with mammary glands, the organs that produce milk to nourish offspring. Mammals generally have hair or fur at least during part of their development, and most give birth to live young rather than laying eggs. The group includes familiar animals such as dogs, cats, elephants, whales, bats, and humans, as well as less immediately recognizable species such as the platypus and echidna. The word is useful in biology and in everyday discussion whenever an animal’s place in the natural world needs to be identified. Although people often think of mammals as large or furry animals, the category also includes marine animals such as dolphins and seals, flying mammals such as bats, and small nocturnal species that may be difficult to observe.
nounA warm-blooded vertebrate that possesses mammary glands and typically gives birth to live young or nourishes its young with milk. Mammals include animals such as whales, bats, elephants, and humans.
- Any animal belonging to the mammalian class, characterized by mammary glands, warm-bloodedness, hair or fur at some stage of development, and usually the production of milk for offspring.
"The blue whale is the largest mammal living on Earth."
"Dolphins are intelligent marine mammals that communicate through clicks and whistles."
"The study of mammals is known as mammalogy."
Use the plural when referring to mammals collectively or to more than one individual. The singular article a is used for one individual.
"Many mammals migrate over long distances."
Humans are mammals, and so are whales, dolphins, bats, and the tiny platypus—one of the few egg-laying mammals.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does mammal come from?
The word entered English in the early modern period from Latin mammalis, meaning “of or relating to the breast.” Latin mammalis derives from mamma, meaning “breast” or “udder,” which also underlies related English words such as mammary. The same Latin family also gives rise to anatomical terms including mammilla and mammillary.
Related word forms
How mammal is actually used
The term is a formal scientific classification and is appropriate in general writing, education, and discussion of biology. In everyday contexts, people may use it to emphasize that an animal is not a bird, reptile, fish, or amphibian.