Duration (noun)

1. The length of time that a situation or event continues.
2. The amount of time between the start and end of an event or situation.

Origin:

Late middle english: from latin duratio(n-), from durare "to last".

Examples:

1. The duration of the storm was brief, lasting only a few hours.
2. The average duration of a marriage in the U.S. is around 8 years.
3. The duration of the movie was two hours and fifteen minutes.
4. The duration of the concert was longer than expected, going on until midnight.
5. The duration of the flight was six hours, with a layover in Chicago.