Middle Dutch is a collective name for a number of closely related West Germanic dialects (whose ancestor was Old Dutch) spoken and written between 1150 and 1500. There was at that time as yet no overarching standard language but they were all mutually intelligible. During this period a rich Medieval Dutch literature developed, not yet present during the period of Old Dutch. The various literary works of that time are often very readable for modern Dutch speakers, since Dutch being a rather conservative language. By many non-linguists, Middle Dutch is often referred to as Diets.