In physics, the definition of time is simple, time is change, or the interval over change occurs. The International System of Units unit for time is seconds, which is abbreviated as s.
We usually deal with elapsed time in physics. To find elapsed time, simply note the beginning time and the ending time and subtract the beginning time from the ending time, so a starting time to 9:00 AM and an ending time of 9:40 AM in the same day would amount to 40 minutes.
Average Velocity is displacement divided by time, and instananeous velocity is the average velocity at a specific instance of time. Speed has no direction, unlike Velocity, so Speed is a Scalar and Velocity is a Vector. Instantaneous speed is the magnitude of instaneous velocity. For example, a teacher with an instaneous velocity of -3.0 m/s would have an instaneous speed of 3.0 m/s. Average speed is the distance traveled divided by elapsed time.