Cadence Chords - What is a common tone?

A common tone is a pitch class that is a member of or related to a musical scale. It sounds complicated, but isn't really. Cadence chords tie into the general idea of a common tone, as they are chords that consist of a changed version of another chord that shares the original chord's common tone. Here are some pictures to help you get an idea of what cadence chords look like:

The original chord of C Major, consisting of C, E, and G, looks like this:

Its first cadence chord, sometimes called the antepenult (even though I've never heard of this name before), consists of B, D, and G, and shares the C Major chord's common tone of G:

Its last cadence chord, consisting of C, F, and A, and sometimes called the final, looks like this, and sharing the C Major chord's common tone of C (I think...):

Thanks to Fiona for taking the great pictures!