Is it ensure, insure, or assure?
late 14c., "action of inducing (someone) to believe (something); argument to persuade, inducement," from Old French persuasion (14c.) and directly from Latin persuasionem (nominative persuasio) "a convincing, persuading," noun of action from past participle stem of persuadere "persuade, convince," from per- "thoroughly, strongly" (see per) + suadere "to urge, persuade," from PIE *swad- "sweet, pleasant" (see sweet (adj.)). Meaning "religious belief, creed" is from 1620s.
the process by which a person's attitudes or behaviour are, without duress, influenced by communications from other people. One's attitudes and behaviour are also affected by other factors (for example, verbal threats, physical coercion, one's physiological states). Not all communication is intended to be persuasive; other purposes include informing or entertaining. Persuasion often involves manipulating people, and for this reason many find the exercise distasteful. Others might argue that, without some degree of social control and mutual accommodation such as that obtained through persuasion, the human community becomes disordered. In this way, persuasion gains moral acceptability when the alternatives are considered. To paraphrase Winston Churchill's evaluation of democracy as a form of government, persuasion is the worst method of social control-except for all the others