A new paradigm for studying auxiliary phenomena is introduced, based on the process of Auxiliary Formation, which correlates their form and function, and is applied to the analysis of the indicative auxiliaries of Tamil. As a result, Auxiliary Formation establishes a grammatical opposition between unmarked simple verbs and marked periphrastic verbs. Application of Auxiliary Formation to Tamil auxiliary verbs reveals that the simple and periphrastic verb forms of the language constitute part of a well-articulated system, not a list of isolated curiosities. Informal usage defines 'auxiliary verb' in contrast to 'main verb', at the minimum, the presence of an auxiliary tends to imply the presence of main verb elsewhere in a structure. However, the reverse need not hold, for many constructions have main verbs without auxiliaries. The auxiliary compound verb is a complex morphosyntactic vehicle that conveys those grammatical categories, or combinations of categories, which happen not to be encoded in any of the basic verbal inflections of the language.