The Collaborative International Dictionary of English v.0.48:
Isotonic \I`so*ton"ic\, a. [Iso- + tonic.]
1. Having or indicating, equal tones, or tension.
2. (Physiology, Biochemistry) Having an osmotic pressure
(tonicity) equal to that of a reference solution; -- of
aqueous solutions. Contrasting with hypotonic and
hypertonic. See hypertonic.
A knowledge of the colligative properties of
solutions . . . is essential for one to understand
fully the principles involved in rendering
intravenous solutions isotonic with blood serum, or
opthalmic solutions isotonic with lachrymal fluid.
Solutions thus adjusted produce less shock and much
less irritation than those which are hypotonic or
hypertonic, and present-day practise recognizes the
desirability of making the necessary adjustments
whenever possible. --Cook &
Isotonic system (Mus.), a system consisting of intervals,
in which each concord is alike tempered, and in which
there are twelve equal semitones.