Final answer:
A certain event in probability theory has a probability of 1 and is guaranteed to happen.
Step-by-step explanation:
A mathematical event that has a probability of 1 is called a certain event. In probability theory, the probability of a certain event occurring is 1, which means it is guaranteed to happen.
For example, if you roll a fair six-sided die, the probability of getting a number between 1 and 6 is 1, since it is certain that the outcome will be one of those numbers. Another example is flipping a fair coin and getting either heads or tails, the probability of this event is also 1.
Certain events have no uncertainty and always happen, making them the most predictable outcomes in probability.
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