pla·​nar·​ia | \ plə-ˈner-ē-ə How to pronounce planaria (audio) \
plural planaria also planarias

Definition of planaria

: any of a genus (Planaria) of 2-eyed planarian worms broadly : planarian

Examples of planaria in a Sentence

Recent Examples on the Web Though often no bigger than an apple seed, planaria are the envy of the animal kingdom. Elizabeth Pennisi, Science | AAAS, 14 June 2018 One hundred and twenty-four of the genes missing from planaria are essential to humans and mice, but the worms seem to do fine without them. John Timmer, Ars Technica, 25 Jan. 2018 More distantly related worms called planaria can be cut into multiple pieces and see each piece regrow an entirely new body. John Timmer, Ars Technica, 25 Jan. 2018 Plenty of other animals can do this — from planaria to newts. David Freeman /, NBC News, 28 Jan. 2018

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

First Known Use of planaria

1855, in the meaning defined above

History and Etymology for planaria

New Latin, from feminine of Late Latin planarius lying on a plane, from Latin planum plane

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The first known use of planaria was in 1855

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Cite this Entry

“Planaria.” Dictionary, Merriam-Webster, Accessed 25 Sep. 2022.

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More Definitions for planaria


pla·​nar·​ia | \ plə-ˈnar-ē-ə, -ˈner- How to pronounce planaria (audio) \

Medical Definition of planaria

1 capitalized : the type genus of the family Planariidae comprising planarian worms having two eyes
2 : any worm of the genus Planaria broadly : planarian


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