ETYM French ton, Latin tonus a sound, tone, from Greek tonos a stretching, straining, raising of the voice, pitch, accent, measure or meter, in pl., modes or keys differing in pitch.
In music, the quality of sound—for instance, different strings of a violin may be able to sound the same note (pitch) given certain fingerings, but each string has a different tone. A tone can also be a plainsong melody; it is also the US term (or wholetone) for a note, an interval consisting of two semitones, for example the interval of C–D.
1. A steady sound without overtones; SYN. pure tone.
2. The quality of a person's voice; SYN. tone of voice.
3. The quality of something (an act or a piece of writing) that reveals the attitudes and presuppositions of the author.
4. A musical interval of two semitones; SYN. whole tone, step, whole step.
5. (Linguistics) A pitch or change in pitch of the voice that serves to distinguish words in tonal languages.

Medicine, tonic medicine; Music, keynote.
A medicine that strengthens and invigorates; SYN. restorative.