A substance with medicinal properties intended to restore or invigorate.

Tonic water.

(figurative) Someone or something that revitalises or reinvigorates.

(music) The first note of a diatonic scale; the keynote.

(music) The triad built on the tonic note.

(phonetics) A tonic element or letter; a vowel or a diphthong.

(physics, pathology) Pertaining to tension, especially of muscles.

Restorative, curative or invigorating.

(medicine, neuroscience) In a state of continuous unremitting action.

(music) Pertaining to or based upon the first note of a diatonic scale.

Pertaining to the accent or stress in a word or in speech.