【正确答案】正确答案：It is differences in pronunciation, grammar, or word choice within a language. Variation in a language may be related to region, to social class and/or educational background or to the degree of formality of a situation in which language is used. For sociolinguists, the most important verity is that a language—any language—is full of systematic variation, variation that can only accounted for by appealing, outside language, to socially relevant force and facts. Sociolinguistics takes as its primary task to map linguistic variation on to social conditions. This mapping helps understand not just synchronic variation(variation at a single point of time), but also diachronic variation(variation over time)or language change.