The linguistic varieties of Modern Greek can be classified along two principal dimensions. First, there is a long tradition of sociolectal variation between the natural, popular spoken language on the one hand and archaizing, learned written forms on the other. Second, there is regional variation between dialects. The competition between the popular and the learned registers (see Diglossia), culminated in the struggle between Dimotiki (Demotic Greek) and Katharevousa during the 19th and 20th centuries. As for regional dialects, variation within the bulk of dialects of present-day Greece is not particularly strong, except for a number of outlying, highly divergent dialects spoken by isolated communities.