-tonia Also -tonic.
Muscle tone or tension; a personality state.
[Greek tonos, tone or tension.]
Examples of the first sense include dystonia (Greek dus-, bad or difficult), a state of abnormal muscle tone resulting in muscular spasm and abnormal posture; hypotonia (Greek hupo, under), a state of abnormally low muscle tone (it can also refer to a condition of lower osmotic pressure); myotonia (Greek mus, mu-, muscle), inability to relax voluntary muscle after vigorous effort. A common example of the second sense is catatonia (Greek kata, badly), abnormal movement and behaviour arising from a disturbed mental state, especially schizophrenia.
Adjectives are formed in -tonic: catatonic, dystonic, myotonic. Some adjectives in this ending do not have analogous nouns in -tonia: isotonic (Greek isos, equal) refers to muscle action that takes place with normal contraction; a person who is syntonic (Greek sun, with) is responsive to and in harmony with their environment.