acquisition is similarly variable, since interlanguage is subject to the same universal and language- specific conventions. In addition, aspects of the second language have been found to be unevenly acquired and are differ­ entially reflected in particular contexts or settings. Yet, despite our expanding knowledge, this variability is only beginning to be treated in much of the sec­ ond-language acquisition literature. This volume presents the work of some researchers and methodologists who have taken on the challenge of including variation in their research designs and pedagogical recommendations. Variation is shown to be relevant to lin­ guistic, social, and psychological aspects of language. It is apparent in the registers and dialects of the target language and in the inter language of learners.