先说一下Social Network这个词，我想可以翻译为社交关系，社交网络或简单的人际关系。来看一下wikipedia的解释：

“A social network is a social structure made of nodes which are generally individuals or organizations. It indicates the ways in which they are connected through various social familiarities ranging from casual acquaintance to close familial bonds. The term was first coined in 1954 by J. A. Barnes (in: Class and Committees in a Norwegian Island Parish, "Human Relations"). The maximum size of social networks tends to be around 150 people and the average size around 124 (Hill and Dunbar, 2002).
社交关系是由一个个体节点或组织构出的社会结构， 这个结构的结识范围可能自己身边熟悉的，或者偶然认识的，最大会有150人，平均124人左右 －查看一下手机列表，聊天列表，好像是有不少人了，即使很少联系的，经常联系的。

Social network analysis ( related to network theory) has emerged as a key technique in modern sociology, anthropology, geography, social psychology, information science and organizational studies, as well as a popular topic of speculation and study. Research in a number of academic fields have demonstrated that social networks operate on many levels, from families up to the level of nations, and play a critical role in determining the way problems are solved, organizations are run, and the degree to which individuals succeed in achieving their goals.

Social networking also refers to a category of Internet applications to help connect friends, business partners, or other individuals together using a variety of tools. These applications, known as online social networks are becoming increasingly popular[1].”

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