1. In terms of solutions:
* Isotonic: A solution with the same osmotic pressure as another solution, typically referring to body fluids.
* Opposite: Hypertonic (higher osmotic pressure) or Hypotonic (lower osmotic pressure).
2. In terms of muscle contraction:
* Isotonic: A contraction where the muscle length changes while maintaining constant tension.
* Opposite: Isometric (muscle contracts but doesn't change length) or Eccentric (muscle lengthens while contracting).
To determine the true opposite, you need to specify the context in which "isotonic" is being used.