EI (written in capital letters) are several more abbreviated names or acronyms for example of Islamic State or Education International.If he is written ei (with lower case) then it may mean anything depending on the topic or issue which concerned. Examples: school independent, entrance inclined, exercise uncomfortable, etc.To be able to better clarify the doubt, it is necessary to know what is the context in which these letters appear to find its meaning.
Latin word: it is the masculine, feminine, and neuter singular dative and the nominative plural masculine is ea id, anaphoric pronoun of the third person, he she it. Unless you want to say hey! in which case it's an interjection indicating call attention, expression of surprise, pleasure etc. equal to eh!, Hey!, Hello!.