Definition of "Tonic" :

noun: a medicine that strengthens and invigorates

noun: (music) the first note of a diatonic scale

noun: a sweet drink containing carbonated water and flavoring

"In New England they call sodas tonics."

noun: lime- or lemon-flavored carbonated water containing quinine

adjective: imparting vitality and energy

adjective: (used of syllables) bearing the principle stress, usually accompanied by a change in pitch

"A tonic syllables carries the main stress in a word."

adjective: relating to or being the keynote of a major or minor scale

"Tonic harmony."

adjective: employing variations in pitch to distinguish meanings of otherwise similar words

adjective: of or relating to or producing normal tone or tonus in muscles or tissue

"A tonic reflex."