Optimism is the attitude or mindset of expecting events to lead to particularly positive, favorable, desirable, and hopeful outcomes. A common idiom used to illustrate optimism versus pessimism is a glass filled with water to the halfway point: an optimist is said to see the glass as half full, while a pessimist sees the glass as half empty. In ordinary English, optimism may be synonymous with idealism—often, unrealistic or foolish optimism in particular.
The term derives from the Latin optimum, meaning "best". To be optimistic, in the typical sense of the word, is to expect the best possible outcome from any given situation. This is usually referred to in psychology as dispositional optimism. It reflects a belief that future conditions will work out for the best. As a trait, it fosters resilience in the face of stress.
