motive

Universal Words noun, adjective noun ~ (for sth) a reason for doing sth: There seemed to be no motive for the murder. * I'm suspicious of his motives. * the profit motive (= the desire to make a profit) * I have an ulterior motive in offering to help you. motiveless adjective: an apparently motiveless murder / attack adjective [onlybeforenoun] (technical) causing movement or action: motive power / force (for example, electricity, to operate machinery)