In this book are five major components of meteorology: (1) thermodynamics, (2) physical meteorology, (3) observation and analysis, (4) dynamics, and (5) weather systems (cyclones, fronts, thunderstorms). Also covered are air-pollution dispersion, numerical weather prediction, and natural climate processes. Starting into the thermodynamics topic now, the state of the air in the atmosphere is defined by its pressure, density, and temperature. Changes of state associated with weather and climate are small perturbations compared to the average (standard) atmosphere. These changes are caused by well-defined processes. Equations and concepts in meteorology are similar to those in physics or engineering, although the jargon and conventions might look different when applied within an Earth framework. For a review of basic science, see Appendix A.