what is synesthesia?

Answer 1

Synesthesia (also spelled synæsthesia or synaesthesia) - from the Greek syn- meaning union and aesthesis meaning sensation, is a neurological condition in which two or more bodily senses are interconnected. For example, in a form of synaesthesia known as grapheme-color synaesthesia, letters or numbers may be perceived as inherently colored. In other forms of synesthesia, musical and other sounds may be perceived as colored or having particular shapes. While artistic metaphors are commonly described as "synesthetic", true neurological synaesthesia is involuntary and believed to be relatively uncommon, occurring in about four percent of the population across its range of variants (see Simner et al., in press).

Answer 2

Its the mixing of the sences. I read a book once called the man who tasted shapes and iit was written by a doctor whose patient experienced synesthesia. The taste of every bit of food he ate had a 'shape' to it.

Answer 3

It's the fusion of sensitive perceptions, induced mostly by psychological stimuli. E.g. you go to Florence, Italy, watch the Cathedral there and suddenly you look at it and it seems to be made out of chocolate. It's because there's a famos pastry shop right in front of it sending chocolate fragrance all over the Cathedral Square.