to·​nus | \ ˈtō-nəs How to pronounce tonus (audio) \

Definition of tonus

: tone sense 9b especially : a state of partial contraction characteristic of normal muscle

Examples of tonus in a Sentence

Recent Examples on the Web The Federal Aviation Agency study notes that kids, especially those under the age of 4, have more flexible skeletons, more relaxed muscle tonus, and a higher proportion of subcutaneous fat, which helps protect internal organs. Dan Koeppel, Popular Mechanics, "Taking a Fall: The 120-MPH, 35,000 Feet, 3-Minutes-To-Impact Survival Guide," 14 Feb. 2021

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

First Known Use of tonus

1876, in the meaning defined above

History and Etymology for tonus

New Latin, from Latin, tension, tone

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Statistics for tonus

Last Updated

26 Feb 2021

Cite this Entry

“Tonus.” Dictionary, Merriam-Webster, Accessed 1 Mar. 2021.

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More Definitions for tonus


to·​nus | \ ˈtō-nəs How to pronounce tonus (audio) \

Medical Definition of tonus

2 : a state of partial contraction that is characteristic of normal muscle, is maintained at least in part by a continuous bombardment of motor impulses originating reflexly, and serves to maintain body posture

called also muscle tone

— compare clonus

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