Agents can't force others to perform a certain action, nor write data onto their internal status. But they can perform communicative actions in order to influence other agents.In Multi-Agent Systems, communication therefore forms a basis for agent interaction as well as social organisation: in the absence of communication,each agent would be closed into its own loop.Thus, it is needed to ensure agents cooperate and coordinate their actions, as well as negotiate in situations of conflict. This makes it possible for tasks to be carried out in a joint manner too.

Most of the communication in Multi-Agent systems is based on the speech act theory, which treats communication as action: it assumes that agents perform speech actions just like any other action, to further their goals and intentions.

There are numerous ways in which the communication can take place, the different modes of communication being classified according to their functions:

• Expressive
  
  This function indicates the state the agent is in,together with its intentions, goals, and the way it visualises things.Very useful in synchronisation, and therefore coordination.


• Conative
  
  Most of the messages in Multi-Agent Systems perform this function, which is the most important one of all, because it refers to a request or demand that a sender will make to the receiving agent.


• Referential
  
  The referential function guarantees the data transmission.


• Phatic
  
  This one is basically used to check whether the channel of communication is working, by establishing, prolonging or interrupting the process.


• Poetic
  
  Compared to all the other functions, this aesthetic function is hardly noticed (if at all), because it just emphasizes the message itself.


• Metalinguistic
  
  Finally, this function is related to a variety of concepts, including the messages being sent, the language being used, as well as the communication situation. It is very important, as it doesn't only enable messages to speak about other messages, but it also allows harmonisation of concepts, vocabulary, and so on. It is further divided into the paralinguistic and metaconceptual sub-functions.