Polydipsia is excessive thirst or excess drinking. The word derives from the Greek πολυδίψιος ("poludípsios") "very thirsty", which is gotten from πολύς ("polús", "much, many") + δίψα ("dípsa", "thirst"). Polydipsia is a symptom in many diseases. It also occurs as a weird behaviour in some animals, such as in birds.