Day

day is the the side of an planet or other object that is in the light of an star.
For example: if earth turns the continent of Europe in the light of our sun, Europe is in day.
Not on every planet is a day as long as on earth(23h 56m 4.09053083288s). On mars, one day is 24 hours, 39 minutes, and 35.244 secondshttp://www.giss.nasa.gov/tools/mars24/help/notes.html.
On mars a 'day' is called: a sol, and more than one sol : sols.
==references==