本书对76种语言时体态的语法语素进行了深入细致的调查，通过跨语言的比较，概括了完成体、进行体及相关语法语素类型以及将来时和部分表示情态的语法语素的语法化路径，深入讨论了语法化理论中的一组假设，总结出语义演变的若干机制。本书还对时体态跨语言研究所涉及到的100个左右的“意义标签”进行了详细的定义和必要的比较。这些定义不仅保证了该研究在跨语言标注时具有较高的内部一致性，而且也为今后的时体类型学研究和语法化研究奠定了基础，对克服时体态研究领域概念混杂的局面起到了很好的澄清作用。概括而言，本书不仅是类型学中时体研究的集大成之作，也是语法化研究的经典著作。

How and why do languages change? This new introduction offers a guide to the types of change at all levels of linguistic structure, as well as the mechanisms behind each type. Based on data from a variety of methods and a huge array of language families, it examines general patterns of change, bringing together recent findings on sound change, analogical change, grammaticalization, the creation and change of constructions, as well as lexical change. Emphasizing crosslinguistic patterns and going well beyond traditional methods in historical linguistics, this book sees change as grounded in cognitive processes and usage factors that are rarely mentioned in other textbooks. Complete with questions for discussion, suggested readings and a useful glossary of terms, this book helps students to gain a general understanding of language as an ever-changing system.