Two events are __?__ events if they are disjoint events and one event or the other must occur.

Answer 1

One or the other must occur means that the two events make up the sample space, like heads and tails in tossing of a coin.

These events are then called complementary. In a Venn diagram, the universal set (&Omega) or sample space is divided into two parts, so that any outcome must fall into one or the other event.