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.
