Definition of tonus in English:

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Pronunciation: /ˈtōnəs/


The constant low-level activity of a body tissue, especially muscle tone.
Example sentences
  • Also, subjacent vascular smooth muscle cells increase their tonus.
  • Since then, I have always remembered the side effects of fentanyl, particularly the increase in sphincter tonus, and all my junior colleagues hear a ‘short lecture’ from me on the subject.
  • Upper airway patency during sleep is determined, in part, by the tonus of pharyngeal dilator muscles.


Late 19th century: from Latin, from Greek tonos 'tension'.

For editors and proofreaders

Syllabification: to·nus

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