What is a Social Network?

A Social Network is a social structure made up of a set of social actors and a set of the dyadic ties between this actors. It perspective provides a set of methods for analyzing the structure of wholea va social entities as well as a variety of theories explaining the patterns observed in these structures.

In the late 1800´s, Émile Durkheim and Ferninand Tönnies foreshadowed the idea of social networks in their theories and research of social groups. Tönnies argued that social groups can exist as personal and direct ties that eather link individual who share values and belief or impersonal, formal and instrumental social links. Durkhaim gave a non-individualistic explanation of social facts, arguing that social phenomena arise when interacting individuals constitute a reality that can no longer be accounted for in terms of the properties of individual actors.
George Simmel, writing at the turn of the twentieth century, pointed to the nature of networks and the effects of network size on interaction and examined the likelihood of interaction in loosely knit networks rather than groups.
In the 1930´s Jacob. L Moreno began systematic recording and analysis of social interaction in small groups, specially classrooms and work groups.
 In anthropology, the foundation for social network theory is the theorical and ethnographic work of Bronislaw Malinowsky, Alfred Radcliffe- Brown and Claude Lévi-Strauss. Max Gluckman, John A. Barnes, J. Clide Mitchell and Elizabeth Bott Spillius performed one of the first fieldworks from which network analysis were performed, investigating community networks in southern Africa, India and the United Kingdom.
In sociology, Talcott Parsons set the stage for taking a relational approach to understanding social structure. Peter Blau provides a strong impetus for analizying the relational ties of social units with his work on social exchange thheory.
Mark Granovetter and Barry Wellman are among the former former student who elaborated and championed the analysis of social networks.

Micro leves of social networks:
- Dyadic level: a dyad is a social relationship between two individual. Network research on dyads may concentrate on structure of the relationship, social equality and tendencies towards reciprocity/mutuality.
 - Tryadic level: research at this level may concentrate on factors such as a balance and transitivity.
- Actor level: the smallest unit of analysis in a social network is an individual in their social setting. This level focuses on social characteristics such as size, strenght, density...
- Subset level: research problems begin at the micro-level such as distance and reachability, cliques...