in early chemistry for water. In Dalton's chemical sign system from the
beginning of the nineteenth century, was the sign
for oxygen, while stood for hydrogen.
Water is a compound of the elements oxygen and hydrogen. In the
earliest chemistry, i.e. alchemy, water as a substance was represented
, and . As one of the four
elements water was often represented by the empty circle in the Middle
Ages. In other contexts, not directly related to chemistry, water
could appear as , , , and .
Compare with , , and , and other signs for different types of rain.