Interaction is a kind of action which occurs as two or more objects have an effect upon one another. It has a tailored meanings in various sciences.

Examples of interaction include:

• communications of any sort. More specific examlple would be two or more people talking to each other, or communications among groups, organisations, nations or states: trade, migration, foreign relations, transportation; etc.
• the feedback during operation of a machines such as a computer or a tool; more specific example would be the interaction between a driver and the position of his or her car on the road: by steering the driver influences this position, by looking this information returns to the driver;

Chemistry and Medicine

In medicine, most medications can be safely used with other medicines but particular combinations of medicines need to be monitored for interactions, often by the pharmacist.

Interactions between drugs fall generally into one of two main categories; pharmacodynamic (involving the actions of the two interacting drugs), and pharmacokinetic (involving the absorption, distribution, metabolism, and excretion of one or both of the interacting drugs upon the other).

Sometimes two or medications are used together to create an extra effect - e.g. two different pain killers to provide more complete pain control. These interactions are usually intentional but need to be monitored by the doctor because patients can end up with more effect than is actually required.

Sometimes two or more medications work against each other. These interactions are usually well-known and avoided unless both medicines are essential. Careful monitoring is used to prevent problems from the results of the interaction.

Other interactions may cause one medicine to have less or more effect than expected and these are usually managed by a dosage adjustment .

Communications

In communications, interactive communication occurs when sources take turns transmitting messages between one another. This should be distinguished from transactive communication, in which sources transmit messages simultaneously.

Physics

In physics, an interaction specifically refers to the action of one physical object upon another - the physical objects under consideration may range from point particles to quantum fields. For example, the interaction of charged particles takes place through the mediation of the electromagnetic field whereas beta decay occurs by means of the weak interaction. There are believed to be four fundamental interactions in nature.

Sociology

In sociology, interaction is a dynamic, changing sequence of social actions between individuals (or groups) who modify their actions and reactions due to the actions by their interaction partner(s).

See also

• Computability logic
• Game semantics
• Interactive computation
• Interaction Design
• Transaction