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• tonic
  tonic

  noun

  a medicine that invigorates or strengthens.
• -tonic
  -tonic

  a combining form occurring in adjectives that correspond to nouns ending in -tonia:

tonic

¹ American  

[ton-ik] / ˈtɒn ɪk /

noun

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.

   Synonyms:

   pickup, bracer, restorative, stimulant

3. quinine water.

4. Music. the first degree of the scale; the keynote.

5. Chiefly Eastern New England. soda pop.

6. Phonetics. a tonic syllable or accent.

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adjective

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. Physiology, Pathology.

   1. pertaining to tension, as of the muscles.

   2. 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. Phonetics. (of a syllable) bearing the principal stress or accent, usually accompanied by a change in pitch.

7. Music.

   1. of or relating to a tone or tones.

   2. pertaining to or founded on the keynote, or first tone, of a musical scale.

      a tonic chord.

-tonic ² American  

1. a combining form occurring in adjectives that correspond to nouns ending in -tonia:

   catatonic.

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tonic British  

/ ˈtɒnɪk /

noun

1. a medicinal preparation intended to improve and strengthen the functioning of the body or increase the feeling of wellbeing

2. anything that enlivens or strengthens

   his speech was a tonic to the audience

3. Also called: tonic water.  a mineral water, usually carbonated and containing quinine and often mixed with gin or other alcoholic drinks

4. music

   1. the first degree of a major or minor scale and the tonal centre of a piece composed in a particular key

   2. a key or chord based on this

5. a stressed syllable in a word

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adjective

1. serving to enliven and invigorate

   a tonic wine

2. of or relating to a tone or tones

3. music of or relating to the first degree of a major or minor scale

4. of or denoting the general effect of colour and light and shade in a picture

5. physiol of, relating to, characterized by, or affecting normal muscular or bodily tone

   a tonic spasm

6. of or relating to stress or the main stress in a word

7. denoting a tone language

Regionalisms

See soda pop.

Other Word Forms

• antitonic
  adjective
• nontonic
  adjective
• pretonic
  noun
• tonically
  adverb

Etymology

Origin of tonic¹

First recorded in 1640–50, tonic is from the Greek word tonikós pertaining to stretching or tones. See tone, -ic

Origin of -tonic²

see origin at tonic

Explanation

A tonic is something, sometimes a medicine, that makes you feel better or restores you to health. Before doctors prescribed drugs, crooked salesmen sold all sorts of dubious tonics. Tonic was used to describe all sorts of concoctions that were supposed to make you feel better or livelier. Some helped and some didn’t. Coca Cola was originally marketed as a tonic — back when it is said to have contained cocaine as well as loads of caffeine. These days we might describe a weekend at the beach or a brisk walk as a tonic, meaning it will refresh you. Others might flee to a gin and tonic — an alcoholic drink.

Example Sentences

You have a lot of cooks and a lot of pots, and you don’t want to get burned in this way again, even if the $300,000 is the perfect tonic.

From MarketWatch • Apr. 21, 2026

What’s Next: The company has also expanded into newer categories, including low-alcohol products like hard seltzers and nonalcoholic beverages such as Hiyo, a tonic drink infused with botanical and functional ingredients.

From Barron's • Jan. 7, 2026

At the start of his finance career, DeAndre Brown, 26, met a mentor during happy hour who taught him the trick of ordering a tonic with lime.

From The Wall Street Journal • Jan. 6, 2026

But numerous online shoppers post product reviews that go further, referring to it as a tonic.

From Salon • Dec. 15, 2025

He was like a salutary tonic; with him, she could only inhabit a higher level of goodness.

From "Americanah" by Chimamanda Ngozi Adichie