precipitation

This word is most often used in weather. It means any form of water that falls from clouds to the ground, such as rain, snow, sleet, hail, or freezing rain. Farmers depend on it, weather reports track it, and too little of it can bring drought while too much can cause floods. The word can also appear in science, where it means a solid forming in a liquid during a chemical reaction, and in formal writing, where it can mean doing something too quickly or suddenly.

Precipitation is most commonly the name for water that falls from the atmosphere to Earth's surface. Rain is the best-known example, but the word also includes snow, sleet, hail, and freezing rain. It is a basic part of the water cycle. Water evaporates from oceans, lakes, rivers, and land, rises into the air as vapor, cools, and forms clouds. When the droplets or ice crystals in those clouds become heavy enough, they fall to the ground.

The type depends on temperature conditions in the air. If the air is warm enough, it falls as rain. If it stays cold, it falls as snow. Sleet forms when partly melted snow or raindrops freeze again before reaching the ground. Hail forms inside strong thunderstorm clouds, where pieces of ice are carried up and down and grow in layers. Because of this, the word is central in weather forecasts, farming, climate studies, and water management.

The word also has other meanings. In chemistry, precipitation is the formation of a solid in a liquid solution during a reaction; that solid is often called a precipitate. In more formal English, precipitation can also mean a sudden or hasty action, especially one taken before enough thought. So while the weather meaning is by far the most common, the word can also describe a chemical change or a rush into action. That gives it a wider story than a simple rainy-day term.