Social contract is a phrase used in philosophy, political science, and sociology to denote a hypothetical agreement within a state regarding the rights and responsibility of the state and its citizens, or more generally a similar concord between a group and its members. All members within a society are assumed to agree to the terms of the social contract by their choice to stay within the society. The term "social contract" was coined by Jean-Jacques Rousseau, in his influential 1762 treatise The Social Contract.
Because social contract theory assumes the existence of a contract binding upon individuals who have not explicitly accepted it, the theory has been found flawed by some philosophers. However, the usual response to this objection is that many contracts and acceptances of same in a modern economy also tend to be implicit, e.g. copyright which exists in a work regardless how marked, entry into private spaces where rules of access and exclusion are posted (but not explicitly accepted other than by actually entering premises), and software and web site licenses. In the same way that implicit contracts in these circumstances standardize interactions to make them simpler and cheaper to support, enhancing the value of capital, social contract can likewise increase the social capital (a formal term for trust), and what's more this is measurable.
In the informal sense of the term, social contracts are informal and many are not well understood. In very dynamic or mobile societies the local consensus is often rapidly shifting as people move in and out of groups. Conflict often arises out of different understandings of the local aggregate expectations as well as disagreement regarding appropriate rules of behavior and interaction. This can be very stressful for group members until new informal agreements have been informally negotiated between interacting members of the group, community, or society.