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

Among hominins and other mammals, females typically exhibit two X chromosomes and males carry an X and a Y chromosome. — Katie Hunt, CNN Money, 24 June 2026

The small insects feed on the blood of mammals. — William Melhado, Sacbee.com, 24 June 2026

More than two decades later, the group's moves are still finding new audiences, including one very large marine mammal. — Anthony Thompson, USA Today, 23 June 2026

An analysis of body masses and maximal running speeds for 100 terrestrial mammals—with typical adult body masses ranging from more than 6,000 kilograms to 16 grams (African elephant to mouse)—found the optimal size for running to be about 120 kilograms, about the size of a mule deer. — Literary Hub, 22 June 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