one day of solar time, the time between successive noons; the time in which a planet such as Earth apparently rotates once around its axis, relative to the sun (on Earth about 24 hours as an average - the length of solar day is not constant throughout the year)
The part of a day in which work is done; the number of hours one must work per day for a specified wage.
Any of those days of a week on which work is done, officially Monday to Friday in many countries (even though many people work on weekends).