In Catalan, Ladino, Latgalian and a number of Slavic languages, i (or і; Ukrainian and Belarusian letter і looks exactly like Latin i) is a conjunction meaning “and”. In Danish, Norwegian, Swedish, Scots, Irish, Hawaiian, Rapa Nui, Tahitian and Tongan it’s a preposition “in”. In Foi language of Papua New Guinea, it may mean “eye”, “seventeen”, or “twenty-one”.
In chemistry, i stands for the Van ’t Hoff factor. In mathematics, i is used to denote
- imaginary unit, i.e. a square root of −1;
- index of summation, used to calculate a sum ∑; or
- index variable in a matrix.