What is the theory of the four "humors"

The word humor actually comes from two words, the Latin word umor and the in medieval word humor, meaning fluid. Both words were medical terms referring temperament or disposition. The theory was that there were four body fluids referred to as humors and these humors were associated with mood: black bile, meaning melancholy; phlegm, meaning apathy; yellow bile, referring to anger; and blood, which was confidence. It was believed that variations in temperaments or illness resulted when the humors were mixed in different quantities. The combination of these body humors resulted in a person being either in good humor or in bad humor.

The ancient Greeks used the term 'humors' to describe a liquid or semiliquid substance in the body. Hippocrates, of ancient Greece, believed in the theory of four'humors' - yellow bile, black bile, phlegm and blood.

The theory holds that good health results when the four humors are in balance. Any imbalance, however, results in an illness or a personality problem.