The term syndrome is used in both medicine and psychology to refer to a group of symptoms or features that occur together in a single person, that have been reported in multiple cases and that are without a known cause.
A syndrome is usually described and identified by a group of characteristics. In some cases there is a requirement that certain of the characteristics must be present for a diagnosis. In other cases the requirements are less stringent.
There are presently more than 340 conditions listed as syndromes.
Many syndromes are named after the person first credited with reporting the condition such as Apert Syndrome and Tourette Syndrome. Others, such as Restless Leg Syndrome, are named after the appearance of the condition.