mono·​treme ˈmä-nə-ˌtrēm How to pronounce monotreme (audio)
: 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 Their bills even include electroreceptors, allowing our humble monotreme to detect living electrical fields produced by its prey. Stephen C. George, Discover Magazine, 29 Aug. 2023 Eventually, after years of study and intense debate, the platypus was classified as a type of primitive mammal known as a monotreme. Stephen C. George, Discover Magazine, 29 Aug. 2023 These trailblazers gave rise to the three mammal lineages that persist today: the egg-laying monotremes; the marsupials, which give birth to feeble young that develop further in a pouch; and the placentals, like Ectoconus and us, which birth larger young. Steve Brusatte, Scientific American, 1 June 2022 That includes all mammals except marsupials (like kangaroos and possums) and monotremes (like platypuses and echidnas). Sarah Leupen, The Conversation, 5 Apr. 2023 With webbed feet, beaver-like tails, duck bills, water-resistant coats and venom-secreting spurs on their hind legs, platypuses might be Australia’s most mysterious and charismatic monotreme, or primitive egg-laying mammals. Theresa MacHemer, Smithsonian Magazine, 28 Jan. 2020 Their unique spot on the evolutionary tree as one of the only two living representatives of the monotreme order (besides echidnas) could even offer insights into the lifestyles of our long-extinct ancestors. Connor Lynch, Discover Magazine, 4 Apr. 2022 But not in the Somalian blind cavefish or placental mammals, which include every mammal aside from five monotreme species (most famously the platypus) and a couple hundred marsupials (kangaroos, koalas, wombats, Tasmanian devils and the like). Gemma Tarlach, Discover Magazine, 11 Oct. 2018 Content includes video, images, and questions designed to teach students about mammals, birds, primates, bears, reptiles, monotremes, marsupials and others. Tracy Maness, Houston Chronicle, 6 Apr. 2020 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'monotreme.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin Monotremata, from Greek mon- + trēmat-, trēma hole — more at trematode

First Known Use

1835, in the meaning defined above

Time Traveler
The first known use of monotreme was in 1835

Dictionary Entries Near monotreme

Cite this Entry

“Monotreme.” Dictionary, Merriam-Webster, Accessed 26 Sep. 2023.

Kids Definition


mono·​treme ˈmän-ə-ˌtrēm How to pronounce monotreme (audio)
: any of an order of egg-laying mammals that include the platypuses and echidnas

Medical Definition


mono·​treme ˈmän-ə-ˌtrēm How to pronounce monotreme (audio)
: any mammal (as a platypus) of the order Monotremata

More from Merriam-Webster on monotreme

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!