A "counterfactual" refers to a concept in which one considers what could have happened if a different decision or event had occurred. It involves imagining alternative scenarios that did not actually take place, often to analyze the impact of specific choices. For example, one might ask, "What if Albert Einstein had never developed the theory of relativity?" Counterfactual thinking is commonly used in various fields, including history, philosophy, and economics. It helps people understand causality and the significance of certain events by exploring how outcomes might have changed under different circumstances.