A timespan is the length of time between two points or the duration of an event. When your teacher assigns a project due in two weeks, that two-week period is the timespan you have to complete it. The timespan of a soccer game is 90 minutes. The timespan of summer vacation might be ten weeks.

The word helps us talk precisely about how long things take or last. Scientists study events across different timespans: a lightning bolt lasts a tiny fraction of a second, while the formation of a mountain range spans millions of years. In your own life, you think in different timespans constantly: the timespan between breakfast and lunch, the timespan of your friend's birthday party, and the timespan until your next dentist appointment.

You might also see this written as two words: time span. Both versions mean exactly the same thing. Writers and editors sometimes prefer one style over the other, but you'll encounter both in books and articles.