Potential Territory

Example  

In the top left White can push through at A, destroying most of Black's potential territory. On the left side, Black has some potential points, which White can take away by placement tactics. On the right side both have potential territory, depending on who gets to play first.

Black has more potential territory in this position but not all of it should be counted as territory that will materialize, since White can take away much of it in sente. Since White has sente now, she can do so and then turn to the right side.

A rule of thumb is to count potential territory as half of its actual potential. This assumes gote everywhere though and the best method, though time consuming, is still to calculate the count according to miai endgame analysis.