Optimism is a mental attitude. A common idiom used to illustrate optimism versus pessimism is a glass with water at the halfway point, where the optimist is said to see the glass as half full and the pessimist sees the glass as half empty. The term is originally derived from the Latin optimum, meaning "best". Being optimistic, in the typical sense of the word, is defined as expecting the best possible outcome from any given situation. This is usually referred to in psychology as dispositional optimism. It thus reflects a belief that future conditions will work out for the best.