This chapter reviews landslide processes and provides a vocabulary for describing landslide features relevant to classification, control, and remediation. It builds on the 1978 landslide report by Varnes, emphasizing progress since then. The term "landslide" refers to the movement of rock, debris, or earth down a slope. The chapter excludes ground subsidence, collapse, snow avalanches, and ice falls. It follows Varnes's intent to refine terminology for precise landslide description. New terms have been added, and some old terms discouraged. The chapter discusses landslide classification, including types of movement (falls, topples, slides, spreads, flows) and materials (rock, debris, earth). A two-noun classification system is used, with examples like "rock fall" or "debris flow." The chapter also introduces the concept of complex landslides and the use of descriptors to identify multiple types of movement. It discusses landslide features, dimensions, and activity states, including active, suspended, dormant, stabilized, relict, and reactivated landslides. The chapter also covers landslide velocity, water content, and material types, providing a framework for understanding and classifying landslides. The terminology used is consistent with the UNESCO Working Party on Landslides (WP/WLI) and other international standards. The chapter emphasizes the importance of precise terminology for effective landslide management and prevention.This chapter reviews landslide processes and provides a vocabulary for describing landslide features relevant to classification, control, and remediation. It builds on the 1978 landslide report by Varnes, emphasizing progress since then. The term "landslide" refers to the movement of rock, debris, or earth down a slope. The chapter excludes ground subsidence, collapse, snow avalanches, and ice falls. It follows Varnes's intent to refine terminology for precise landslide description. New terms have been added, and some old terms discouraged. The chapter discusses landslide classification, including types of movement (falls, topples, slides, spreads, flows) and materials (rock, debris, earth). A two-noun classification system is used, with examples like "rock fall" or "debris flow." The chapter also introduces the concept of complex landslides and the use of descriptors to identify multiple types of movement. It discusses landslide features, dimensions, and activity states, including active, suspended, dormant, stabilized, relict, and reactivated landslides. The chapter also covers landslide velocity, water content, and material types, providing a framework for understanding and classifying landslides. The terminology used is consistent with the UNESCO Working Party on Landslides (WP/WLI) and other international standards. The chapter emphasizes the importance of precise terminology for effective landslide management and prevention.