monotreme

noun

mono·​treme ˈmä-nə-ˌtrēm 

: any of an order (Monotremata) of egg-laying mammals comprising the platypuses and echidnas

Examples of monotreme in a Sentence

Recent Examples on the Web

Both animals, known as monotremes, are the only mammals that lay eggs. —Ashley Strickland, CNN Money, 4 May 2025

The humerus bone unearthed in the 1990s dates back to between 103 million and 108 million years ago, and is the only fossil example of the extinct monotreme Kryoryctes cadburyi. —Margherita Bassi, Smithsonian Magazine, 1 May 2025

Nevertheless, monotremes can help scientists better understand the earliest stages of mammalian evolution, says Guillermo Rougier, a researcher in anatomical sciences and neurobiology at Kentucky’s University of Louisville who also wasn't involved in the study. —Margherita Bassi, Smithsonian Magazine, 1 May 2025

There are relatively few fossils of Mesozoic era monotremes. —Paul Smaglik, Discover Magazine, 28 Apr. 2025

Word History

Etymology

borrowed from French monotrème, from mono- mono- + -trème, borrowed from Greek trēmat-, trêma "aperture, hole"; so named because members of the order have a single orifice for both excretory and reproductive functions — more at trematode

Note: The name was introduced by the French naturalist Étienne Geoffroy Saint-Hilaire (1772-1874) in "Extrait des observations anatomiques de M. Home, sur l'echidné," Bulletin des sciences, par la Société Philomathique, no. 77 (Thermidor, An 11 [July, 1803]), pp. 225-26. The word was subsequently latinized as a plural taxon Monotremata.

First Known Use

1835, in the meaning defined above

Rhymes for monotreme

• academe
• cherubim
• elohim
• episteme
• seraphim
• abeam
• airstream
• bloodstream
• daydream
• downstream
• esteem
• extreme

Kids Definition

monotreme

noun

mono·​treme ˈmän-ə-ˌtrēm 

: any of an order of egg-laying mammals that include the platypuses and echidnas

Medical Definition

monotreme

noun

mono·​treme ˈmän-ə-ˌtrēm 

: any mammal (as a platypus) of the order Monotremata