This document defines and provides examples of discourse communities. It begins by asking questions about discourse communities and their importance. It then defines discourse communities as groups that work towards common goals through communication and share genres, vocabulary, and levels of expertise. John Swales' six characteristics of discourse communities are outlined. Examples provided include Christianity, a sorority, and an honors college. The document explains how discourse communities relate to rhetorical situation, genre, intertextuality, and the importance of understanding the discourse community when writing. It concludes with advice on using discourse communities to guide writing.