Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or pess opaque bluish-white color. Ice is used in a variety of ways, including cooling, winter sports and ice sculpture. Ice can be found on the oceans, land and structures, on rivers and streams, on lakes, and even sometimes in the air.

The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the cryosphere. Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and snowpacks are an important storage mechanism for fresh water; over time, they may sublimate or melt. Snowmelt is an important source of seasonal fresh water. The World Meteorological Organization defines several kinds of ice depending on origin, size, shape, influence and so on.[43] Clathrate hydrates are forms of ice that contain gas molecules trapped within its crystal lattice.