Sponsored by the Association for Educational Communications and Technology (AECT), this book presents a definition of the field of study and practice known as educational technology or instructional technology. It reflects the collaborative efforts of all members of the AECT Definition and Terminology Committee. This revised volume begins with the statement of the definition itself (chapter 1), followed by commentary chapters on each of the key terms and concepts contained in the definition (chapters 2-9). Chapter 10 provides historical context for the current definition by reviewing salient elements of prior AECT definitions. Chapter 11 discusses ethical considerations and chapter 12 concludes by discussing ramifications of the current definition for academic programs in educational technology. This book is appropriate for anyone working in the field of educational technology: students, instructors, researchers, and in-service providers.