A perlocutionary act (or perlocutionary effect) is a speech act, as viewed at the level of its psychological consequences, such as persuading, convincing, scaring, enlightening, inspiring, or otherwise getting someone to do or realize something. This is contrasted with locutionary and illocutionary acts (which are other levels of description, rather than different types of speech acts)[1].
Unlike the notion of locutionary act, which describes the linguistic function of an utterance, a perlocutionary effect is in some sense external to the performance. It may be thought of, in a sense, as the effect of the illocutionary act via the locutionary act. Therefore, when examining perlocutionary acts, the effect on the hearer or reader is emphasized.
As an example, consider the following utterance: "By the way, I have a CD of Debussy; would you like to borrow it?" Its illocutionary function is an offer, while its intended perlocutionary effect might be to impress the listener, or to show a friendly attitude, or to encourage an interest in a particular type of music.