Keys are show in yellow using letters. The letter alone indicates a major key, if followed by an m, a minor key.
In the example we show the C major, B flat major and A minor keys.

Roman numerals in lowercase correspond to degrees with minor triads

Degrees with diminished triads

Triads in first inversion

Triads in second inversion

Sevent chords in root position

Seventh chord in first inversion

Seventh chord in second inversion

Seventh chord in third inversion

Dominanth ninth chord

Minor dominanth ninth chord

Dominant ninth chord in first inversion

Secondary dominant and diminished sevent chords

Neapolitan sixth chord

Italian augmented chord

German augmented chord

A first degree seventh chord in first inversion with an augmented fifth

Diminished sevent chord with a common note to the dominant chord to which it resolves. This chord has no standard name in traditional harmony and theorist rarely talk about it although it is very common. Walter Piston calls it a II degree seventh chord with raised root and third. We use the term appoggiatura diminished seventh. We could also use the term common note diminished seventh.
Example from the Sonata: