Iota

Iota (uppercase/lowercase Ι ι), is the letter of the Greek alphabet, used to represent the "i" sound in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 10. Letters that came from it include the Roman I and Cyrillic І.
In mathematics, the lowercase formula_1 is used to represent the inclusion function in set theory. The term "iota" is also used to refer to an infinitesimal amount or an insignificant quantity.