"Discussions abound about how to properly differentiate formal and informal learning. To make things even more complicated, some throw in the notion of non-formal learning as a further refinement. On the one hand, the distinction has been made loosely to differentiate between learning in schools (formal) and all the other learning (informal). As long as you don't think to deeply, this works. However, now that some want to start theorizing about informal learning (workplace learning, professional learning, ...) and environments are claimed to be developed for it (such as MOOCs), too loose a definition won't do anymore. I will make a suggestion here for a sharp distinction that is simple to apply yet allows us to continue most of the conversations about formal and informal learning that we have engaged in."

Via Andreas Link