Duration

Duration is the amount of time between the beginning and end of an event or interval. It is distinct from the event’s start time or end time.

Time: Time is the dimension in which events occur in sequence and durations can be measured. Duration measures separation along this dimension.
Clock time: Clock time is time measured or represented by a clock’s readings. It expresses duration through changes in clock indications.
Stopwatch: A stopwatch is a timekeeping instrument designed to measure the elapsed time of an event. It measures event duration directly from start to finish.
Timestamp: A timestamp is a recorded designation of a specific date or time. A timestamp locates an event; duration measures the span between events.
Time interval: A time interval is the portion of time bounded by two temporal points. A duration is the length assigned to such an interval.
Proper time: Proper time is the time measured by a clock following a particular path through spacetime. Relativity makes measured duration depend on the clock’s path.
Reaction time: Reaction time is the interval between a stimulus and a measurable response. It applies duration measurement to behavior and perception.
Frequency: Frequency is the number of occurrences of a repeating event per unit time. Frequency describes repetition rate, unlike the length of one interval.
Instant: An instant is a point in time with no duration. An interval’s boundary instants determine its elapsed duration.
Time dilation: Time dilation is the difference in elapsed time measured by observers in relative motion or different gravitational fields. It shows that duration can vary between observers.

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