Meteorology (from Greek: μετέωρον, metéōron, "high in the sky"; an λόγος, lógos, "knowledge") is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting (in contrast with climatology). Meteorological phenomena are observable weather events which illuminate and are explained by the science of meteorology. Those events are bound by the variables that exist in Earth's atmosphere. They are temperature, pressure, water vapor, and the gradients and interactions of each variable, and how they change in time. The majority of Earth's observed weather is located in the troposphere.