This introductory chapter outlines what a cycle is, what kinds of cycles are generally accepted, and how the contributions in this book fit the various cycles. Uncontroversial cycles are the negative, future, modal, and determiner cycles; these will be referred to as micro-cycles. More controversial are macro-cycles, i.e. cycles that shift a language from analytic to synthetic and from synthetic to analytic. These cycles are controversial partly because of the use of the terms analytic and synthetic, which will be discussed briefly. The introduction also includes a section on recent work, issues of debate, and on future directions.