Definition: A syndrome could be a set of symptoms and clinical signs (clinical syndrome), a set of lesions (lesional syndrome), a set of malformations (malformative syndrome) or a set of biological anomalies (biological syndrome).

Syndromes and Nosology

One of the main problems with nosologies is that diseases often cannot be defined and classified clearly especially when pathogenesis or causality is not known. So, diagnostic terms often are in fact only symptoms or sets of symptoms (syndromes).