Ice is the solid state of water. The term can also be used with an adjective, to indicate an ice-like substance that is the solid state of some other material that is normally liquid or gas (e.g., dry ice). The term water ice is sometimes used to avoid ambiguity.
Ice consists of water molecules (two hydrogen atoms covalently bonded to an oxygen atom) with hydrogen bonds (electrostatic bond, a bond between oppositely-charged ions) to the oxygen atom of another molecule. Ice is essentially water molecules stuck to each other (the type of adsorption called physisorption).
Ice can be amorphous or crystalline.
Ices (water and other types) and their detection are of interest in cosmology and in study of cool clouds as some molecules are expected to exist in the form of ice on dust grains in such clouds.