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1. (used of solutions) having the same or equal osmotic pressure
   - isosmotic
    
2. Relating to or characterized by the equal intervals of a musical scale
   "isotonic tuning"
    
3. (physiology) of or involving muscular contraction in which tension is constant while length changes
    
4. (physiology) of two or more muscles; having equal tension

See also: tense

Antonym: hypertonic, hypotonic, isometric

Encyclopedia: Isotonic