It is an event that can occur once.1 pointUnion EventObjective probabilitySubjective probability

It seems like you're asking for definitions of the terms "Union Event", "Objective Probability", and "Subjective Probability". Here they are:

1. Union Event: In probability theory, a union event refers to the occurrence of at least one of two or more possible events. If we have two events A and B, the union of A and B is the set of all outcomes that are in A, or in B, or in both.

2. Objective Probability: This is a type of probability that is based on factual and measurable data. It is not influenced by personal beliefs or opinions. For example, the probability of getting a head when you flip a fair coin is 0.5, which is an objective probability.

3. Subjective Probability: This is a type of probability that is based on personal judgment or opinion. It is not strictly based on mathematical calculations or measurable data. For example, if someone thinks that it will rain tomorrow based on their interpretation of the sky's appearance, this is a subjective probability.