This document provides definitions of organization development (OD) from several experts and outlines the historical development and current practice of OD. It also outlines the structure of the book, which examines the process of OD including entering and diagnosing organizations, designing and implementing interventions, and addressing areas like human processes, techno-structural changes, human resources management, and strategic interventions. The goal of OD is to improve an organization's ability to solve problems and adapt to changes through behavioral science approaches and planned interventions.