Sleep pattern: The rythm in which one rests and wakes. Usually this takes the form of going to sleep in the evening and waking in the morn', but international travel and noding can put a serious dent in it. Supposedly it is healthy to have a regular (that is, non-changing) sleep pattern, if you don't, your body will adjust to get the equivalent of eight hours of sleep per night. This might mean taking an hour nap in the afternoon or not sleeping one night and sleeping 10 hours for the next four.