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

Their descendants began to diversify into the ancestors of modern amphibians and amniotes–the group that includes birds, reptiles, and mammals. —Laura Baisas, Popular Science, 14 May 2025

One possibility is that intelligence in vertebrates—animals with backbones, including mammals and birds—evolved once. —Yasemin Saplakoglu, Wired News, 11 May 2025

They’ve been detected in the guts and tissues of many marine animals such as mammals, seabirds, turtles, zooplankton, fish, and sharks. —Melissa Cristina Márquez, Forbes.com, 1 May 2025

Scientists earlier showed that Ronan, a resident of the Long Marine Laboratory at the University of California, Santa Cruz, was the first nonhuman mammal who could be trained to keep a beat, including moving in time with music. —Gennaro Tomma, New York Times, 1 May 2025

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