Social interaction is a dynamic, changing sequence of social actions between individuals (or groups) who modify their actions and reactions according to those of their interaction partner(s). In other words, they are events in which people attach meaning to a situation, interpret what others are meaning, and respond accordingly. Social interactions can be differentiated into: Accidental (also known as social contact) - not planned and likely not repeated. For example, asking a stranger for directions or shopkeeper for product availability. Repeated - not planned, bound to happen from time to time. For example, accidentally meeting a neighbour 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, playing a game, etc.), family, etc. In sociological hierarchy, social interaction is more advanced than behaviour, action, social behaviour, social action and social contact, and is in turn followed by more advanced concept of social relation. In other words, social interactions, which consist of social actions, form the basis for social relations. This handbook presents the latest international research in the field.