This book covers the essentials of modality and offers both foundational ideas and cutting edge advances. The book consists of what are essentially tutorials on modality and modal notions, covering definitions of modality, morphosyntactic form, conceptual and logical semantics, historical development, and acquisition. There are also specific chapters on modality in Zapotec and American Sign Language, which show the range of forms that modal notions can take. To assist its tutorial function, the book closes with a comprehensive conceptual outline of all the chapters.