Names are given to the degrees of the notes in the scales in music. Unusual names you might say, including Tonic and Supertonic- not to be confused with a gin menu or herbal remedy!
Tonic, supertonic, mediant, subdominant, dominant, submediant, leading note (and return to tonic or octave). For example, in C major, the tonic note C is followed in order by D,E,F,G,A, and B. Do note, that when using chords (triads) there are minor and diminished chords as well as majors. (See chart below for examples).
You can use these names of degrees to refer to the main chords in a key. For example, a simple song in C major may use the 3 chords: C, F and G majors. Otherwise known as tonic, subdominant and dominant (1, 4 and 5 degrees of the scale).
Often degrees of the scale are applied when identifying music modulating into other keys as well as naming cadences or chord progressions. For example, a piece of music written in A minor may modulate to its subdominant key (D minor) or dominant key (E minor) before resolving back to the original tonic (A minor).
A perfect cadence (or perfect chord resolve) may be referred to as a 5-1 chord or ‘dominant-tonic’ rather than stating letters (for example, G-C in the key of C major). For this reason, it is worthwhile knowing and being able to identify these titles given when learning music theory. The names of the degrees never change so can be used in any key. Examples below are shown for C major and A minor.
Other valuable supporting concepts include chord charts for each major and minor key as well as the circle of fifths and cadence types. Learning scales, chords and arpeggios or broken chords can therefore prove invaluable at understanding how music is put together using these terms of identification and is transferable knowledge which can be applied when playing in any key of music.
Essentially, when learning any instrument it is worthwhile to make sense of how music is made and how the melody and harmony are structured, rather than merely playing or listening to music without being able to recognise melodic or chord patterns. Music theory can open a whole other dimension when analysing music and composing it.