The cuneiform i sign is a common use vowel sign. It can be found in many languages, examples being the Akkadian language of the Epic of Gilgamesh (hundreds of years, parts of millenniums) and the mid 14th-century BC Amarna letters; also the Hittite language-(see table of Hittite cuneiform signs below).
As i and one of the four vowels in Akkadian (there is no "o"), scribes can easily use one sign (a vowel, or a syllable with a vowel) to substitute one vowel for another. In the Amarna letters, the segue adverb "now", or "now, at this time", Akkadian language 'en?ma', is seldom spelled with the 'e'; instead its spellings are typically: an?ma, in?ma, and sometimes en?ma. In both the Amarna letters and the Epic of Gilgamesh another common use of the "i" sign is for the preposition, Akkadian language ina, spelled i-na, for in, into, for, etc.. (There is an alternate cuneiform sign for ina (cuneiform), a sub-variety use of a? (cuneiform), the single, horizontal stroke.)