Most commonly used in healthcare, but in increasingly broad use in other fields, a syndrome is a grouping of observable phenomena that, when taken together, identify a particular problem. In medicine, these observations include symptoms recounted by a patient or otherwise obtained in a medical history, signs on examination, and the result of laboratory (e.g., clinical chemistry, hematology, microbiology) and imaging tests. Often, syndromic diagnosis proceeds step-by-step, as one observation suggests the need for additional investigation. The word comes from the Greek for "run together", as the phenomena are assessed to be related.
A syndrome is a set of manifestations, and, at least in the preliminary phases of diagnosis, there can be different etiologies for the presentation. Other than to suppress unpleasant manifestations, a firm etiology must be determined before rational medical treatment can proceed.
Many syndromes are eponyms, named for the clinician that first described them, such as Korsakoff's syndrome or Asperger syndrome. Other syndrome names are descriptive of the presentation, such as acquired immune deficiency syndrome or metabolic syndrome. Syndromes may be named for the etiology (e.g., acute radiation syndrome).