As a Noun: 1. A period of time which is at least one full day (twenty four hours) after the time of speaking. 2. A period of time which is at least one full day (twenty four hours) after a reference time already established in the past or future. As Modifier: 1. Used at the beginning of a sentence or immediately next to a verb to mean the action takes place one full day (twenty four hours) after the time of speaking or the reference time. English = one day later, a day from now, in a day's time.