This study deals with variation in grammar both from a theoretical and an empirical point of view. In Part I (Chaps. 1-4), an attempt is made to char acterize this phenomenon within the broader context of what might be called the "fluctuating character of natu'ral language," and to develop suitable and precise descriptive techniques that account for it. The method which is pro posed here is called "variety grammar" - roughly speaking, this is a formal grammar with probabilistic weighting for an ordered set of varieties, such as dialects, sociolects, registers, or developmental stages. In Part...