"Synesthesia is the general name for a related set (a "complex") of various cognitive states. Synesthesia may be divided into two general, somewhat overlapping types. The first, which I sometimes call "synesthesia proper", is as described above, in which stimuli to a sensory input will also trigger sensations in one or more other sensory modes. The second form of synesthesia, called "cognitive" or "category synesthesia", involves synesthetic additions to culture-bound cognitive categorizational systems. In simpler words, with this kind of synesthesia, certain sets of things which our individual cultures teach us to put together and categorize in some specific way – like letters, numbers, or people's names – also get some kind of sensory addition, such as a smell, color or flavor....
"Synesthesia is additive; that is, it adds to the initial (primary) sensory perception, rather than replacing one perceptual mode for another...." Sean A. Day
My synesthesias include:
Sound to touch and sight (texture stronger than color)
Sight to touch
Ticker tape: When I speak, hear others speak, or think in words, I "see" the words written out. Note: It seems to never been in the same typeface twice in a row.
Much of my thinking is in kinesthetic/tactile/visual diagrams in three or four dimensions; occasionally five dimensions.