This book is about the possibilities and achievements of children, adolescents and adults who have developmental disorders that make their development of speech difficult or very delayed and who therefore need to develop communication and language with other means than speech.For some, the difficulties are temporary in childhood, others continue to communicate with alternative communication systems throughout adulthood. This comprehensive and accessible volume offers guidance based on current knowledge about typical and atypical language development for all those supporting families and professionals involved with children, adolescents and adults who may benefit from using augmentative and alternative communication (AAC) systems. The text covers all major issues and gives a thorough introduction to factors that are important when choosing communication systems, vocabularies of manual signs and graphic symbols.It guides the reader in assessment strategies, adaptation of the language environment, and the principles for teaching comprehension and use of AAC, sentence formation and conversational skills to individuals with different disabilities, including motor disabilities, intellectual disabilities, autism spectrum disorders and developmental language disorders.The volume also addresses the influence of AAC on speech development and the use of AAC to promote participation in various activities, including social media, and to reduce challenging behaviour. The book will be essential reading for students and practising psychologists, speech and language therapists, special educators, teachers, physiotherapists and occupational therapists.The accessible guidance will also be helpful for the families of children, adolescents and adults who use augmentative and alternative communication.