This chapter reviews the range of landslide processes and provides a vocabulary for describing landslide features relevant to their classification for avoidance, control, or remediation. It emphasizes the progress made since Varnes' 1978 report, minimizing departures from his classification. The chapter focuses on the terminology used to describe landslides, including the types of movement and materials involved. It retains Varnes' terms largely unchanged while adding new terms and refining existing ones. The chapter also discusses the criteria for classifying landslides, emphasizing the type of movement and material. It provides a detailed classification system for landslide features and dimensions, including definitions and methods for measuring them. The chapter further explores the states, distribution, and styles of landslide activity, and introduces a modified scale for estimating landslide velocity and its destructive significance. The goal is to provide a comprehensive and precise vocabulary for describing landslides, aiding investigators and practitioners in understanding and managing landslide risks.This chapter reviews the range of landslide processes and provides a vocabulary for describing landslide features relevant to their classification for avoidance, control, or remediation. It emphasizes the progress made since Varnes' 1978 report, minimizing departures from his classification. The chapter focuses on the terminology used to describe landslides, including the types of movement and materials involved. It retains Varnes' terms largely unchanged while adding new terms and refining existing ones. The chapter also discusses the criteria for classifying landslides, emphasizing the type of movement and material. It provides a detailed classification system for landslide features and dimensions, including definitions and methods for measuring them. The chapter further explores the states, distribution, and styles of landslide activity, and introduces a modified scale for estimating landslide velocity and its destructive significance. The goal is to provide a comprehensive and precise vocabulary for describing landslides, aiding investigators and practitioners in understanding and managing landslide risks.