Stint
A stint is the run of laps a driver completes on one set of tyres, between pit stops.
Race strategy is really a plan for how many stints to run and how long each should be. A one-stop race is two stints, a two-stop is three.
Pace within a stint is not flat: a tyre is quickest early and degrades, so a driver's lap times drift as it ages. The point at which the loss exceeds the cost of a pit stop is when the stint should end.