Polydipsia is a noun that refers to excessive thirst. 

The Greek word for thirst forms the basis for our word of the day and it’s joined by its prefix P-O-L-Y, which, in this context, means ‘very much.’ Polydipsia has been around since the mid-17th century. It’s often used in a medical context, but can also be used in an informal setting. Example:

After two hours in the Nevada sun, I was ready to guzzle down a gallon of iced tea. I haven’t experienced this kind of polydipsia since I spent a summer in Central America.