A pattern of social interaction, having a relatively stable structure, that persists over time. Institutions have structural properties - they are organized - and they are shaped by cultural values. Thus, for example, the institution of marriage, in western societies, is structurally located in a cohabiting couple and regulated by norms about sexual exclusiveness, love, sharing, etc.
There is not full agreement about the number or designation of social institutions in a society but the following would typically be included: family, economy, politics, education, health care, media.
A social institution which encompasses the individual, cutting them off from significant social interaction outside its bounds. These institutions are frequently involved in the process of resocialization whereby individuals are detached from their previous sense of identity and re-shaped to accept and absorb new values and behavior. Examples include religious orders, prisons and army training camps.
The condition of a group within a larger society where the major institutions -- economy, politics, family, schooling, -- are reproduced thus enabling the smaller group to have little social connection with the larger group.
Where social interaction is predictably patterned within relatively stable structures regulated by norms. For example, seeking a diagnosis for a physical illness or obtaining advise or a cure is institutionalized within the health care institution.
Conflict over values or interests is institutionalized within the 'political system'.
Sexual access and raising children is institutionalized within the family.