Synesthesia (or synaesthesia) is loosely defined as "senses coming together," which is just a translation of the Greek (etymology: syn - together, esthesia from aesthesis - sensation). At its simplest level, synesthesia means that when a certain sense or part of a sense is activated, another unrelated sense or part of a sense is activated concurrently. For example, when someone hears a sound, he or she immediately sees a color or shape in his or her "mind's eye." People that have synesthesia are called synesthetes