What is cause? What is cause? The producer of an effect, result, or consequence.The one, such as a person, event, or condition, that is responsible for an action or result.A basis for an action or response; a reason: The doctor's report gave no cause for alarm. A goal or principle served with dedication and zeal: "the cause of freedom versus tyranny” ( Hannah Arendt). The interests of a person or group engaged in a struggle: "The cause of America is in great measure the cause of all mankind” ( Thomas Paine). Law A ground for legal action.Law A lawsuit.A subject under debate or discussion.To be the cause of or reason for; result in.To bring about or compel by authority or force: The moderator invoked a rule causing the debate to be ended.