IOTA is a Roman letter, which is the ninth letter of the Greek alphabet. It is also known as the 'i' sound in English and is represented by the symbol ι. In mathematics, it is used to represent the imaginary unit, which is the square root of -1. In physics, it is used to represent the electric current. In chemistry, it is used to represent the isotope of an element. In astronomy, it is used to represent the smallest star in a constellation.