This book presents a detailed corpus-based study of adverbial subordinate clauses in English within the framework of the theory of Functional Grammar. On the basis of an in-depth data analysis, this study shows that there is a systematic correlation between the semantic types of adverbial clauses, on the one hand, and the verb forms by means of which these constructions are expressed in English, on the other. In contrast to most traditional classifications, the criterion used for the semantic classification of adverbial clauses is not simply the basic meaning of the conjunction introducing the subordinate clause. Instead, the present classification is based on the systematic and consistent application of four semantic parameters: Entity Type, Time Dependency, Factuality and Presupposition. The relevance of the application of these parameters is not only that they allow to establish a complete and exhaustive typology of adverbial clauses, but also that they form the basis for four implicational hierarchies that determine the distribution of expression formats along the different semantic types of adverbial clauses. This book also constitutes a contribution to the application of Functional Grammar to the corpus-based analysis of a specific language and, more specifically, to the validation of the hierarchical model of the structure of the clause postulated within this theoretical framework.