Which term refers to an abnormal increase in thirst?

The term that refers to an abnormal increase in thirst is polydipsia. This medical terminology is derived from the Greek word "dipsa," which means thirst. Polydipsia is often a symptom associated with various medical conditions, such as diabetes mellitus, where the body's inability to manage blood sugar levels leads to dehydration and consequently increased thirst.

The other terms do not relate to thirst. For instance, polyuria refers to excessive urination, which can sometimes accompany polydipsia in certain health conditions. Normocephalic describes a normal head shape and size, and febrile refers to having a fever, typically indicating an illness or infection. Understanding these definitions helps clarify why polydipsia specifically denotes an increase in thirst.