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

Swimmer's itch is a skin rash caused by an allergic reaction to microscopic parasites that infect some birds and mammals, according to the Centers for Disease Control and Prevention. —Jalen Williams, Freep.com, 11 July 2025

Lefebvre has been studying harmful algae blooms for her entire career and was involved in the first-ever study in 1998 that found domoic acid was impacting marine mammals in Central California. —Julia Jacobo, ABC News, 9 July 2025

Nictitating membranes act as a type of third eyelid going horizontally across the eye and found in some animals like birds, reptiles and some mammals. —Irene Wright july 8, Miami Herald, 8 July 2025

The city is home to 1,600 species of plants, 5,200 insects, around 100 birds, 40 mammals, and 30 reptile and amphibian species. —Krista Langlois, Smithsonian Magazine, 7 July 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