A revolutionary is a person who either participates in, or advocates for, a revolution. The term revolutionary can also be used as an adjective to describe something producing a major and sudden impact on society.

In political science, a reactionary or a reactionist is a person who holds political views that favor a return to the status quo ante—the previous political state of society—which the person believes possessed positive characteristics that are absent from contemporary society. As a descriptor term, reactionary derives from the ideological context of the left–right political spectrum. As an adjective, the word reactionary describes points of view and policies meant to restore a status quo ante.