Berger and Luckmann introduced the term "social construction" into the social sciences and were strongly influenced by the work of Alfred Schütz. Their central concept is that people and groups interacting in a social system create, over time, concepts or mental representations of each others' actions, and that these concepts eventually become habituated into reciprocal roles played by the actors in relation to each other. When these roles are made available to other members of society to enter into and play out, the reciprocal interactions are said to be institutionalized. In the process, meaning is embedded in society. Knowledge and people's conceptions (and beliefs) of what reality is become embedded in the institutional fabric of society. Reality is therefore said to be socially constructed.