DIALECTOLOGY. The study of DIALECTS, that is, of variant features within a language, their history, differences of form and meaning, interrelationships, distribution, and, more broadly, their spoken as distinct from their literary forms. The discipline recognizes all variations within the bounds of any given language; it classifies and interprets them according to historical origins, principles of development, characteristic features, areal distribution, and social correlates. The scientific study of dialects dates from the mid-19c, when philologists using data preserved in texts began to work out the historical or diachronic development of the Indo-European languages. Their interest was etymological and systematic. Scientific phonetics and the principle that sound change was not erratic but followed discoverable rules or laws, were a basic part of the growth of dialectology. Living dialects were seen to furnish a huge treasury of living data on phonology, lexicology, and other features of language that written texts could not furnish. The linguist's task was to gather, analyse, and interpret this living body of language. Dialectology is pursued through a number of methods; the American linguist W. Nelson Francis (Dialectology, 1983) describes the prevailing methods as traditional, structural, and generative.

In traditional dialectology the collection of data is the primary requirement. This entails fieldwork, the more detailed and massive the better, within the limits of practicability, and its presentation in the form of dictionaries, grammars, atlases, and monographs. This method Francis calls ‘item-centered’, emphasizing the individual datum and paying little attention to underlying system. In structural dialectology, the investigator seeks to find both the structure or system by which a dialect holds together or achieves synchronic identity and how it is changed by the introduction of any new feature. Since any change in the system affects every feature of it, it becomes in effect a different system, whose parts are, however, diachronically connected. There is a paradoxical element here which is partly due to difficulties of definition. In generative dialectology, the investigator holds that the language exists within the speaker as a competence which is never fully realized in performance. This competence, lying beneath actual language as it is produced (and as it is recorded by traditional dialectologists), works by a series of rules which transform it into actual speech. Thus, it is the dialectologist's task to find a basic system whose rules produce as economically as possible the surface structure of actual dialect. The complexities or variations within a language (its dialectal variants) may thus be traced back to a putative source form from which in the course of time they could by speciation have developed. However, without the mass of data which traditional dialectologists have furnished, theoretical systems could not have been either proposed or refined.