Tropical cyclones are the deadliest tropical weather systems. This chapter describes their seasonal and geographic variability and controls, decadal cycles, and history of naming conventions. Tropical cyclogenesis is explored in depth and the core and balance solutions for regions of the cyclone are examined. Intensity is considered in terms of inner-core dynamics, large-scale environmental controls, limits on potential intensity, satellite interpretation techniques, and classification by wind speed. Factors that influence motion are investigated. Extratropical transition is described in terms of structural changes, preceding mechanisms, and impact on high latitudes. Societal impacts and mitigation are also covered.