mammal

noun

mam·​mal ˈma-məl 

: 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

mammalian

mə-ˈmā-lē-ən 

ma-

adjective or noun

mammal-like

ˈma-məl-ˌlīk 

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

When discriminating a living agent, many animals, particularly mammals, observe their behavior to figure out another being’s intentions and anticipate future actions. — Literary Hub, 14 Aug. 2026

Although people sometimes use animals informally to mean only vertebrates (animals with backbones) or even just mammals, in biology the term includes insects as well. — Encyclopedia Britannica, 14 Aug. 2026

Between March and June, the mammals’ typical mating season, the no-go zone increases to 500 meters (1,640 feet). — Charlotte Reck, CNN Money, 14 Aug. 2026

Quanta spoke with Cao about evidence for the programmed theory of aging, what happens at each stage, and why aging mammals are like trees shedding leaves. — Ingrid Wickelgren, Quanta Magazine, 14 Aug. 2026

Word History

Etymology

from base of New Latin Mammalia (Linnaeus), class name, noun derivative from neuter plural of mammālis, from Latin mamma "breast, udder" + -ālis -al entry 1 — more at mamma entry 1

First Known Use

1811, in the meaning defined above

Rhymes for mammal

• camel
• hamel
• hamil
• trammel
• enamel
• glutamyl

Kids 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

mammal

noun

mam·​mal ˈmam-əl 

: any of the higher vertebrate animals comprising the class Mammalia

mammalian

mə-ˈmā-lē-ən, ma- 

adjective or noun