When we express ourselves linguistically, it is often to convey information or to make statements. We do this by describing conventional facts, such as: Water freezes when a temperature of max. 0°C is reached. Statements of this kind can be recognized by the fact that they can be classified as true or false. We can therefore judge the latter utterance either as true “yes, that is right”, or false “no, that is not right”. Nevertheless, we can do much more with language than just describe or claim: we can act with language. When a linguistic utterance becomes an action, we call it a speech act. Such utterances can be triggered by performative words or certain forms of expression. Performative words describe a section embedded in several word groups - in most cases within verbs. Those so-called performatives embody an action within their expression. Examples are: promise, swear, bet, warn etc. Putting these at use, with the statement: I promise that I will be home before midnight! one automatically commits oneself to an action, i.e. with the announcment of the promise the action is already accomplished. Performative statements can also be recognized by the fact that they can neither be described as true nor as false. So if someone says to you I promise that I will be home before midnight! You cannot reply "That's not true, you don't promise me that", because the person has already promised you with their statement, regardless of whether they will keep or break their promise in the future. 

Besides verbs, other word groups can also include performatives: I hereby sentence you to three years in prison. The word hereby takes on a formal and performative role and is used to declare a sentence as valid. The necessary condition here is that the person speaking has the official authority and permission to perform the act of sentencing someone to a punishment. This kind of speech act is only successful if the above criterion is met. For instance, if that very judgment was to be expressed by an industrial worker to their superior, the speech act would be considered unsuccessful, due to the speaker’s lack of valid authority. On the other hand, if a judge uttered this statement at the end of a court case, the judgment would be considered valid. 

Speech acts can also occur when certain forms of expression are used. This refers to expressions such as commands, wishes, questions or threats etc. The following example shows two utterances that can be classified as speech acts due to their forms of expression.

(1) Enno, leave the room!
(2) If Enno leaves the room, I will leave too. 

Both examples are about a person named Enno, and it is reported in both cases that Enno might leave the room. Despite sharing common clues, the two statements have a different effect and imply different actions. While the first sentence represents a clear command, the second utterance embodies a threat. It is likely that the result of both is that Enno will leave the room. In statement (2), however, another person, namely the one uttering the threat, will leave the room together with Enno. Thus, the form of expression causes different actions and reactions. 

Basically, we distinguish between direct and indirect speech acts. The former express exactly what they mean i.e. they reflect what is to be achieved. The latter, on the other hand, carry an indirect statement in addition to the linguistic utterance. Let us consider this issue by means of an example, where (a) and (b) represent two possible speech acts, each of which could occur independently in the situation described:

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Class 4B is sitting in a classroom. It is snowing outside and Mika opens the window to let in some fresh air. In response, Toni calls out:

(a) Close the window, it's cold!
(b) Brrrr! It's so cold!

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By means of statement (a), it is directly and unmistakably expressed that Toni is freezing and therefore the window should be closed. Statement (b), on the other hand, expresses primarily that Toni feels cold. From the context, and thus as an indirect request, we understand that Toni intends with his exclamation to get Mika to close the window again. Thus, it becomes clear that indirect speech acts are also actions and can trigger an associated reaction.