ABCDEFGHIJKLMNOPQRSTUVWXYZ Definition of Hour more ... A period of time equal to 1/24 (a twenty-fourth) of a day. 1 Day = 24 Hours 1 Hour = 60 minutes. Example: The amount of time between 5:00 and 6:00 is one hour. ../measure/images/clock-drag.js?w=300 See: Minute The Time - Converting AM/PM to 24 Hour Clock