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variants:
or less commonly Bayes theorem or less commonly Bayes's theorem

## Definition of *Bayes' theorem*

**:**a theorem about conditional probabilities: the probability that an event A occurs given that another event B has already occurred is equal to the probability that the event B occurs given that A has already occurred multiplied by the probability of occurrence of event A and divided by the probability of occurrence of event B

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Merriam-Webster unabridgedWords at Play

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Bayes' theoremTime Traveler for

Bayes' theorem## The first known use of

Bayes' theoremwas in 1830See more words from the same year