ce·​ta·​cean | \ si-ˈtā-shən How to pronounce cetacean (audio) \

Definition of cetacean

: any of an order (Cetacea) of aquatic mostly marine mammals that includes the whales, dolphins, porpoises, and related forms and that have a torpedo-shaped nearly hairless body, paddle-shaped forelimbs but no hind limbs, one or two nares opening externally at the top of the head, and a horizontally flattened tail used for locomotion

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Other Words from cetacean

cetacean adjective
cetaceous \ si-​ˈtā-​shəs How to pronounce cetaceous (audio) \ adjective

Examples of cetacean in a Sentence

Recent Examples on the Web

Orcas, dolphins and other cetaceans have made for popular attractions at some aquatic theme parks for decades, but their presence has raised concerns about the ethics of confining whales for the purposes of human entertainment. Anchorage Daily News, "With ‘Free Willy’ bill, Canada bans captivity and breeding of whales and dolphins," 11 June 2019 But researchers recently started referring to an entire class of non-fish seafood that includes cetaceans, other marine mammals and marine reptiles, as aquatic bushmeat. Craig Welch, National Geographic, "More people are eating marine animals—with deadly results," 22 May 2019 Such assessments are of interest to us, and researchers around the globe, with current investigations focused on wildlife such as arboreal mammals and cetaceans. Smithsonian, "When It Comes to Counting Wildlife, Drones Are More Accurate Than People," 27 Feb. 2018 These recent, extreme adaptations raise a question of how cetaceans may continue to change. Brian Switek, Smithsonian, "Today’s Whales Are Huge, But Why Aren’t They Huger?," 27 June 2018 The study showed cetaceans with the largest brain size relative to their body living in more complex groups or pods were more likely to show grief. Jason Daley, Smithsonian, "Study Suggests Dolphins and Some Whales Grieve Their Dead," 20 June 2018 Similar results have been found in other families of mammals, like ungulates (deer, camels, and the like) and cetaceans (whales and dolphins). Cathleen O'grady, Ars Technica, "The evolutionary mystery of gigantic human brains," 23 Aug. 2018 Indeed, there is evidence that many cetaceans—that is, whales, dolphins and porpoises—have strong and complicated family and social ties. Alison Gopnik, WSJ, "Like Us, Whales May Be Smart Because They’re Social," 16 Aug. 2018 Among marine mammals, pinnipeds, such as seals, do—but cetaceans, such as whales and dolphins, do not. Anna Diamond, Smithsonian, "Do Marine Mammals Yawn and More Questions From Our Readers," 28 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cetacean.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of cetacean

1835, in the meaning defined above

History and Etymology for cetacean

ultimately from Latin cetus whale, from Greek kētos

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cetane number


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Last Updated

17 Jun 2019

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Time Traveler for cetacean

The first known use of cetacean was in 1835

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English Language Learners Definition of cetacean

technical : a mammal (such as a whale, dolphin, or porpoise) that lives in the ocean

More from Merriam-Webster on cetacean

Britannica.com: Encyclopedia article about cetacean

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