The Wikipedia article on social software defines it this way: “Social software encompasses a range of software systems that allow users to interact and share data.” Clay Shirky defines it this way: “It’s software that supports group interaction.”

in the modern web-based context, social software creates emergent network effects resulting from scale and self-organization that produce the true value of the software to its users. Modern social software produces emergence when its use is widespread. It creates global attributes and patterns at the system level that are truly novel. The definition of social software I’ll use is: software that supports group interaction, and creates emergent network effects resulting from increasing scale and from the self-organization the software enables and supports.