Answer:
Although illocutionary acts are commonly made explicit by the use of performative verbs like "promise" or "request," they can often be vague as in someone saying "I'll be there," wherein the audience cannot ascertain whether the speaker has made a promise or not.
In addition, as Daniel R. Boisvert observes in "Expressivism, Nondeclarative, and Success-Conditional Semantics" that we can use sentences to "warn, congratulate, complain, predict, command, apologize, inquire, explain, describe, request, bet, marry, and adjourn, to list just a few specific kinds of illocutionary act."The terms illocutionary act and illocutionary force were introduced by British linguistic philosopher John Austin in 1962's "How to Do Things With Words, and for some scholars, the term illocutionary act is virtually synonymous with speech act.
Locutionary, Illocutionary, and Perlocutionary Acts
Acts of speech can be broken down into three categories: locutionary, illocutionary, and perlocutionary acts. In each of these, too, the acts can either be direct or indirect, which quantify how effective they are at conveying the speaker's message to its intended audience.
