Locutionary, illocutionary and perlocutionary acts
In his investigation of the force of linguistic expressions, Austin distinguished between three types of act present in every utterance, the locutionary, illocutionary and perlocutionary acts. He defined them as follows:
• locutionary act: the act of saying something;
• illocutionary act: the act performed in saying something; and
• perlocutionary act: the act performed by saying something.
What do these definitions mean? The locutionary act – the act of saying something – is the act of expressing the basic, literal meanings of the words chosen. For example, in uttering the words You will get your hands blown off, a speaker performs the locutionary act of stating that the hearer will get their hands blown off. The illocutionary act is the act that the speaker performs in saying something. In many contexts, utterance of the statement You will get your hands blown off is intended, and understood, as an act of warning: the utterance thus has the illocutionary force of a warning. Thanking, congratulating, and advising are all acts which differ in their illocutionary force; in all of them, the speaker does more than describe or assert facts about some situation. As Austin puts it, the speaker of this type of act does not simply say something, instead, (s)he does something (thank, congratulate, or advise) by engaging in a certain conventionalized form of verbal behaviour. Illocutionary acts are also referred to as speech acts. Lastly, the perlocutionary act is the act of producing an effect in the hearer by means of the utterance. Depending on the circumstances, the perlocutionary act involved in saying You will get your hands blown off might be to dissuade the hearer from playing with a lighter and a stick of dynamite, to frighten the hearer, to encourage them to go on pro vocatively waving a naked flame in front of a bag of fi reworks, etc.
The linguistic expressions which figure in illocutionary acts do not simply have the function of describing or stating facts about a situation (this Austin called the constative function). When we say something like You will get your hands blown off, we are not only stating something: we are also performing an action, the action of warning. If it was not obvious that the words You will get your hands blown off were intended to constitute a warning, the speaker could explicitly say I’m warning you, you’ll get your hands blown off. In using the verb warn, the speaker makes the force of their utterance as a warning explicit; there is, indeed, no other way to explicitly warn someone other than to use the words ‘I’m warning you’, ‘I warn you that’, or synonymous constructions. Austin called this type of utterance an explicit performative utterance: when I say I warn you that . . . I am not describing or stating the existence of any independent fact; I am, instead, performing an act (the act of warning) which cannot be explicitly performed in any other way. (By contrast, the basic utterance you will get your hands blown off may well have the illocutionary force of a warning, but it is not an explicit performative; we will call it an implicit performative.)
It would be impossible to provide a full catalogue of all the illocutionary (or speech) acts which may be performed in English. As well as asserting, questioning and ordering, a very modest list would include promising, thanking, requesting, congratulating, greeting, advising, naming, swearing, scolding, apologizing, guaranteeing and warning. All these are particular conventionalized ways of using language which we recognize as associated with a particular repertoire of conditions and responses. In order for a speaker S to request a hearer H to perform an act A, for example, a particular set of social conditions needs to be fulfilled. Searle’s summary of these conditions appears in (1):

QUESTION Consider the following sentences, and label them as always performative (P), possibly performative (PP), or never performative (NP). For the first two categories, state whether they are explicitly performative or not:

QUESTION Consider the following sentences. What illocutionary acts could they realize?
I’m glad you’re here. Take your time. I’m allergic to milk. Was that the doorbell? Don’t worry about putting out the rubbish.