pla·​nar·​i·​an plə-ˈner-ē-ən How to pronounce planarian (audio)
: triclad
especially : any of various dark-colored freshwater triclad flatworms (family Planariidae) with two eyespots and a triangular head

Examples of planarian in a Sentence

Recent Examples on the Web This capacity is all too evidently lacking in humans—so how do planarians do it? Philip Ball, Scientific American, 18 Apr. 2023 Even a small part of a planarian can regenerate into a full worm with the typical shape and proportions. Philip Ball, Scientific American, 18 Apr. 2023 Cut off a planarian's head, and the creature will simply sprout a new one in its place. Marla Broadfoot, Discover Magazine, 25 Nov. 2015 So how did the the planarian lose its centrosomes? Elizabeth Preston, Discover Magazine, 10 Jan. 2012 If one animal could become an honorary superhero, my vote would be for the planarian. Seriously Science, Discover Magazine, 15 July 2013 Even so, this planarian and its beady eyespots is cute enough to take your breath away. Christie Wilcox, Discover Magazine, 3 Sep. 2015 With no new ones to replace them, the planarian has a few weeks to live. Ed Yong, Discover Magazine, 12 May 2011 Researchers led by Wallace Marshall at the University of California, San Francisco, wanted to know how centrosomes were involved in the amazing regenerative abilities of this planarian. Elizabeth Preston, Discover Magazine, 10 Jan. 2012

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'planarian.' 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 Planaria

First Known Use

1854, in the meaning defined above

Time Traveler
The first known use of planarian was in 1854

Dictionary Entries Near planarian

Cite this Entry

“Planarian.” Dictionary, Merriam-Webster, Accessed 19 Apr. 2024.

Kids Definition


pla·​nar·​i·​an plə-ˈnar-ē-ən How to pronounce planarian (audio)
: any of an order of small soft-bodied mostly water-dwelling flatworms having cilia
especially : one living in fresh water and having two eyespots and a triangular head

Medical Definition


pla·​nar·​i·​an -ē-ən How to pronounce planarian (audio)
: any of the family Planariidae or order Tricladida comprising small soft-bodied ciliated mostly aquatic turbellarian worms
planarian adjective

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