i.e. = id est [Latin] = that is it is used for clarification: "That is (to say)" in the sense of "that means" and "which means", or "in other words", or sometimes "in this case", depending on the context; may be followed by a comma, or not, depending on style (American English and British English respectively). It is often misinterpreted as "in example". In this situation, e.g. should be used instead. not to be confused with e.g. = exempli gratia [Latin] = 'for the sake of example' = for example