The concept you're describing is known as complementary events in probability. Two events are considered complementary when they are mutually exclusive, meaning that the occurrence of one event implies that the other cannot occur, and together they encompass all possible outcomes of a probabilistic experiment.
For example, when flipping a coin, the event of getting heads and the event of getting tails are complementary events because:
- If the coin lands on heads, it cannot land on tails, and vice versa.
- Together, they account for all possible outcomes of the coin flip.
Another example could be rolling a six-sided die:
- The event of rolling an even number (2, 4, or 6) and the event of rolling an odd number (1, 3, or 5) are complementary events as well, as one cannot roll both an even and an odd number in a single die roll.
In summary, complementary events are distinct events that cover all potential outcomes of a random experiment without overlapping.