Definition
Time interval
A time interval is the amount of time from one stated moment or event to another.
What it means
Mark a start and an end. The time that passes between those two marks is the interval. You can count forward from the start or subtract the earlier clock time from the later one when both times use the same reference.
Remember it
Two time marks make a gap; the time-sized gap is the interval.
Example
A lesson starts at 10:15 and ends at 10:50. Counting forward gives 15 minutes to 10:30 and 20 more minutes to 10:50, so the time interval is 35 minutes.
Watch for
A start time such as 10:15 is a clock reading; the interval is the duration from that reading to an end time.
Common mix-up
When finding elapsed days, count the jumps between dates, not just the date labels you can name.
Exact meaning
A time interval is the duration between two specified instants or events, expressed in a unit of time.