tonic

Concise Oxford English Dictionary © 2008 Oxford University Press:
tonic/ˈtɒnɪk/

▶noun

• 1 a medicinal substance taken to give a feeling of vigour or well-being.

• 2 something with an invigorating effect.

• 3 (also tonic water) a carbonated soft drink with a bitter flavour, used as a mixer with gin or other spirits.

• 4 Music the first note in a scale which, in conventional harmony, provides the keynote of a piece of music.

▶adjective

• 1 Music relating to or denoting the first degree of a scale.

• 2 Phonetics denoting or relating to the syllable within a tone group that has greatest prominence.

• 3 Physiology relating to or restoring muscle tone.

  ■ of or denoting continuous muscular contraction.

– derivatives
tonically adverb.

– origin C17: from Fr. tonique, from Gk tonikos ‘of or for stretching’, from tonos (see tone).