IPA: //ˈsuːpərˌtɒnɪk//
KK: /ˈsuːpərˌtɒnɪk/
The second note in a scale of music, which follows the tonic note.
In the key of C major, D is the supertonic note.
Supertonic → It is formed from "super-" (meaning above or over) and "tonic" (from Latin "tonicus", meaning having to do with tone or tension). The word "supertonic" refers to a note that is above the tonic in a scale, thus relating to the concept of being above in musical context.
Think of 'super-' meaning 'above' and 'tonic' relating to 'tone' — so a supertonic is a note that is above the main tone.