Pronunciation: (ton'ik),[key] —n. 1. a medicine that invigorates or strengthens: a tonic of sulphur and molasses. 2. anything invigorating physically, mentally, or morally: His cheerful greeting was a real tonic. 3. See quinine water. 4. Music.the first degree of the scale; the keynote.
5. Chiefly Eastern New Eng.soda pop.
6. Phonet.a tonic syllable or accent.
—adj. 1. pertaining to, maintaining, increasing, or restoring the tone or health of the body or an organ, as a medicine.
2. invigorating physically, mentally, or morally.
3. Physiol.,Pathol. a. pertaining to tension, as of the muscles.
b. marked by continued muscular tension: a tonic spasm. 4. using differences in tone or pitch to distinguish between words that are otherwise phonemically identical: a tonic language. 5. pertaining to tone or accent in speech.
6. Phonet.(of a syllable) bearing the principal stress or accent, usually accompanied by a change in pitch.
7. Music. a. of or pertaining to a tone or tones.
b. pertaining to or founded on the keynote, or first tone, of a musical scale: a tonic chord.
a combining form occurring in adjectives that correspond to nouns ending in -tonia:catatonic.