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 grant, from the National Fish and Wildlife Foundation, would allow the tribes to work with other Native groups and advocacy organizations to come up with a working plan to reintroduce the marine mammals in Oregon, likely from existing populations in Washington. —Kale Williams, Axios, 29 Jan. 2025

The previous bones in the series came from marine mammals. —Brooke Baitinger, Sacramento Bee, 29 Jan. 2025

These same regions are also home to 70% of the forest birds in mainland China, 70% of its forest mammals and 31% of forest amphibians, according to a 2015 Duke University study. —Christopher Cann, USA TODAY, 26 Jan. 2025

While rare, mammals including dogs and cats can be infected with avian flu, mainly through coming into contact with wild birds or eating infected pet food, according to the American Veterinary Medical Association. —Stephen Underwood, Hartford Courant, 24 Jan. 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

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