Practical definition for piano: third means either skip two keys or skip three keys. Consider what you get when you play two white keys by skipping one, either playing one then the other going either way, or both together. Read further at your own risk!
- The intervals that are white notes use only white piano keys. Those that are black notes use at least one black piano key.
- 3rds use three letters. Their “size” depends on how many keys we skip.
- A diminished 3rd skips one key. It is also a whole-step.
- A minor 3rd skips two keys. It is also a whole-step + a half-step.
- A Major 3rd skips three keys. It is also two whole-steps.
- An augmented 3rd skips four keys. It is also two whole-steps + a half step.