What is Synesthesia?

You know the word 'anesthesia' which means no sensation; well 'synesthesia' means joined sensation. And what is joined is two, three, or all five senses together. So that my voice, for example, to a synesthete is not just something that they hear, but also something that they see, or smell, or touch.

Music for example is not just a sound and a melody, but it's like a visual fireworks that they see in front of them on a little screen, rather than in the mind's eye.

As per a recent phone conversation where the subject came up, here's the answer about Hannah and her special ability: Also is Kinda Crunchy.