What is the meaning of tonic?

noun

• Lime- or lemon-flavored carbonated water containing quinine.
  • synonyms: tonic water, quinine water
• A sweet drink containing carbonated water and flavoring.
  • usage: "in New England they call sodas tonics"
  • synonyms: pop, soda, soda pop, soda water
• Music) the first note of a diatonic scale.
  • synonyms: keynote
• A medicine that strengthens and invigorates.
  • synonyms: restorative

adjective

• Of or relating to or producing normal tone or tonus in muscles or tissue.
  • usage: "a tonic reflex"; "tonic muscle contraction"
• Employing variations in pitch to distinguish meanings of otherwise similar words.
  • usage: "Chinese is a tonal language"
  • synonyms: tonal
• Used of syllables.
  • usage: "a tonic syllables carries the main stress in a word"
  • synonyms: accented
• Relating to or being the keynote of a major or minor scale.
  • usage: "tonic harmony"
• Imparting vitality and energy.
  • usage: "the bracing mountain air"
  • synonyms: bracing, brisk, fresh, refreshing, refreshful