Social software is any software that supports group communications. The dynamics of social software are significantly different from traditional interactions.
Social Software and the Politics of Groups, Clay Shirky, First published March 9, 2003 on the "Networks, Economics, and Culture" mailing list (http://www.shirky.com/writings/group_politics).
... various other European, Middle Eastern, and Asian immigrant groups who have settled in Brazil since the mid-19th century; and indigenous people of Tupi and Guarani ...