A substance with medicinal properties intended to restore or invigorate. / Tonic water. / (US, Eastern Massachusetts) Any of various carbonated, non-alcoholic beverages; soda pop.

(medicine, archaic) To restore or invigorate.

(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.

(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.

(uncountable) A simple cocktail made from gin and tonic water, often served on ice and with a slice of lime or lemon. / (countable) A glass of the above.

A carbonated beverage containing quinine, originally used as a prophylactic against malaria, and now used as a soft drink or as a mixer in gin and tonic and other cocktails.

(geology) Of a geologic period within the Neoproterozoic era from about 1000 to 850 million years ago.

(geology) The Tonian period.

(rare, intransitive) To thunder.

(US, informal, entertainment industry) Alternative spelling of tonight