1. They are not the V and I chords. This is the most basic definition of a cadence, and it excludes any other pairs of chords.
2. They do not create a sense of resolution or finality. Cadences typically mark the end of a phrase or section of music, and they do this by creating a sense of resolution. If a pair of chords does not do this, it is not a cadence.
3. They are not in the right context. Cadences are typically used at the end of phrases or sections of music, but they can also be used in the middle of a phrase to create a sense of anticipation. However, if a pair of chords is not used in a context where it can create a sense of resolution or anticipation, it is not a cadence.
Here are some examples of pairs of chords that are not cadences:
* The I and IV chords. This pair of chords is often used in the middle of a phrase to create a sense of anticipation.
* The V and IV chords. This pair of chords can create a sense of resolution, but it is not as strong as the V and I cadence.
* The I and vi chords. This pair of chords can create a sense of finality, but it is not as strong as the V and I cadence.
In general, a pair of chords is only a cadence if it meets all three of the criteria listed above.