Ton"ic (?), a. [Cf. F. tonigue, Gr. &?;. See Tone.]
1.
Of or relating to tones or sounds; specifically (Phon.), applied to, or distingshing, a speech sound made with tone unmixed and undimmed by obstruction, such sounds, namely, the vowels and diphthongs, being so called by Dr. James Rush (1833) " from their forming the purest and most plastic material of intonation."
2.
Of or pertaining to tension; increasing tension; hence, increasing strength; as, tonic power.
3. (Med.)
Increasing strength, or the tone of the animal system; obviating the effects of debility, and restoring healthy functions.
Tonic spasm. (Med.) See the Note under Spasm.
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Ton"ic, n. [Cf. F. tonique, NL. tonicum.]
1. (Phon.)
A tonic element or letter; a vowel or a diphthong.
2. (Mus.)
The key tone, or first tone of any scale.
3. (Med.)
A medicine that increases the strength, and gives vigor of action to the system.
Tonic sol-fa (Mus.), the name of the most popular among letter systems of notation (at least in England), based on key relationship, and hence called "tonic." Instead of the five lines, clefs, signature, etc., of the usual notation, it employs letters and the syllables do, re, mi, etc., variously modified, with other simple signs of duration, of upper or lower octave, etc. See Sol- fa.
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Ton"ic, a. (Med.)
Characterized by continuous muscular contraction; as, tonic convulsions.
© Webster 1913