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

The giant, 10,000-pound mammals provided meat, fat, hide, and bones for building structures, as well as ivory for tools, art, and ornaments. — Laura Baisas, Popular Science, 30 July 2026

Large white sharks migrate from the open Pacific toward the coast beginning in October to feed on marine mammals and typically remain through January. — Ethan Baron, Mercury News, 30 July 2026

During the 2015-16 season, for instance, Dungeness crabs off the coast of California were infected by a harmful algal bloom of Pseudo-nitzschia, which causes domoic acid poisoning in crabs, fish, birds and marine mammals. — Susanne Rust follow, Los Angeles Times, 29 July 2026

Every mammal has borders between haired and hairless skin, and those borders are drawn early, in the embryo, when skin cells decide whether to build a hair follicle. — Scott Travers, Forbes.com, 28 July 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