Definition
Hour
An hour is a time interval equal to exactly 60 minutes or 3600 seconds.
What it means
Think of one hour as one complete 60-minute block. 'Three hours' tells how long; 'three o’clock' tells when.
Remember it
One hour is a full ring of 60 minutes.
Example
A lesson starts at 9:15 and lasts 2 hours. Adding two 60-minute blocks gives an end time of 11:15.
Watch for
An hour measures duration; a clock reading such as 4:00 names a time of day.
Common mix-up
1 hour 30 minutes is 90 minutes, not 1.30 hours.
Exact meaning
An hour (h) is a unit of duration equal to 60 minutes, which is 3600 seconds. Clock-hour labels also help name times of day, but a time of day is not itself a duration.