syn-, sy-, sym-, syl-, sys-

1. A condition in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces the visualization of a color.
2. A sensation felt in one part of the body as a result of stimulus applied to another, as in referred pain.
3. The description of one kind of sense impression by using words that normally describe another.
4. A condition in which normally separate senses are not separated.

Characteristics of synesthesia

Sight may mingle with sound, taste with touch, etc. The senses are cross-wired; for example, when a digit-color synesthete sees or just thinks of a number, the number appears with a color film over it.

A given number's color never changes; it appears every time with the number. Synesthesia can take many forms. A synesthete may sense the taste of chicken as a pointed object. Other synesthetes hear colors. Still others may have several senses cross-wired.

Estimates of the frequency of synesthesia range from 1 in 250,000 to 1 in 2,000. People with synesthesia are six times more likely to be female than male. Most synesthetes find their unusual sensory abilities enjoyable.

People with synesthesia often report that one or more of their family members also have synesthesia, so it may in at least some cases be an inherited condition.

It may be that synesthesia arises when particular senses fail to become fully independent of one another during normal development. According to this school of thought, all babies are synesthetes.

Synesthesia can be induced by certain hallucinogenic drugs and can also occur in some types of seizure disorders

The words synesthesia is a hybrid of Latin and Greek and comes from Latin syn-, "together" + -esthesia, from the Greek aisthesis, "sensation" or "perception".

One example of synesthesia

Daniel Tammet is a high-functioning autistic savant. He can calculate huge sums in his head in seconds and instantaneously recognise prime numbers. One of fewer than fifty such people living worldwide, Daniel is unique in his ability to articulate his savant experience.

He describes his visual experience of numbers as complex synaesthetic shapes with colour, texture, and motion. Thirty-seven is lumpy like porridge, while eighty-nine reminds him of falling snow. Sequences of digits form visual landscapes in his mind.

The feeling of sensation in one part of the body when another part is stimulated.

Someone who experiences synesthesia, as by having a secondary sensation of sound as color or of color as sound.