Interaction

Interaction is a kind of action which occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction instead of a one-way causal effect. Combinations of many simple interactions can lead to surprising emergent phenomena. It has different tailored meanings in various sciences.

Casual examples of interaction outside of science include:


 * communication of any sort, for example two or more people talking to each other, or communication 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, for example 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. In molecular biology, the knowledge on gene/protein interaction among themselves and with their metabolites is referred to as molecular pathways.

Interactions between medications 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.

Media Art
In media, interactivity is a feature of the media in question and as digital technology becomes more accessible to the masses interest in interactivity is increasing and becoming a cultural trend especially in the arts. Interactivity can exist in virtual spaces or in real space. With virtual interaction the interaction usually takes place in the space of a computer with the monitor providing visual cues and the keyboard and mouse allowing interaction. In physical space the interaction usually involves sensors, actuators and computer systems with code that allow interactive systems to respond to human position, touch and sound.

Physics
In physics, an interaction or force specifically refers to the action of one physical object upon another and results in a potential energy - 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 electromagnetic fields, whereas beta decay occurs by means of the weak interaction. There are believed to be four fundamental interactions in Nature.

Sociology
In sociology, social 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). Social interactions can be differentiated into:
 * accidental - not planned and likely not repeated. For example, asking a stranger for directions or shopkeeper for product availabity.
 * repeated - not planned, bound to happen from time to time. For example, accidentally meeting a neighbour from time to time when walking on your street;
 * regular - not planned, but very common, likely to raise questions when missed. Meeting a doorman or a security guard every workday in your workplace, dining every day in the same restaurant, etc.
 * regulated - planned and regulated by customs or law, will definitely raise questions when missed. Interaction in a workplace (coming to work, staff meetings, etc.), family, etc.

Social interactions form the basis for social relations.