prob·a·bil·i·ty | \ˌprä-bə-ˈbi-lə-tē \
plural probabilities

Definition of probability 

1 : the quality or state of being probable

2 : something (such as an event or circumstance) that is probable

3a(1) : the ratio of the number of outcomes in an exhaustive set of equally likely outcomes that produce a given event to the total number of possible outcomes

(2) : the chance that a given event will occur

b : a branch of mathematics concerned with the study of probabilities

4 : a logical relation between statements such that evidence confirming one confirms the other to some degree

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Synonyms & Antonyms for probability


liability, likelihood


improbability, unlikelihood, unlikeliness

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Examples of probability in a Sentence

There is a low probability that you will be chosen. There is some probability of rain tomorrow. With the dark clouds moving in, rain seems more like a probability than a possibility. The probability of a coin coming up heads is one out of every two tries.
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Recent Examples on the Web

Sixth, as explained more fully below, Michigan State is mindful that a longer litigation against Nassar’s victims would have increased the probability that damaging emails and other records surface. Michael Mccann,, "Michigan State Settles With the Victims of Larry Nassar's Abuse. How Might the NCAA Respond?," 18 May 2018 On Sunday evening, NWS meteorologist Matt Doody told the Globe that the storm models appear to be moving further west, which slightly increases the probability that snow could accumulate in southeast New England. Jaclyn Reiss,, "Everything you need to know about the potential midweek nor’easter," 19 Mar. 2018 The agency says there is zero probability of impact for about a third of Earth’s surface. Jason Daley, Smithsonian, "Five Things to Know About China’s Falling Space Station," 9 Mar. 2018 According to data presented by, there is a 1 percent probability of rain on June 11. Weldon B. Johnson, azcentral, "Rain in Phoenix on June 11? That would be a first," 11 June 2018 Of these, families with a higher probability of tearing into each other over the turkey did indeed prove more likely to leave early. Lydia Denworth, Scientific American, "Thanksgiving Dinner May End Sooner If Guests Pass the Gravy across a Partisan Divide," 1 June 2018 In all probability, either the FBI or Russian intelligence has gotten to her. Jonathan Chait, Daily Intelligencer, "Will Trump Be Meeting With His Counterpart — Or His Handler?," 8 July 2018 Well, gee, susceptible to injury, shouldn’t that have entered into some decision in the past?’ And the answer to that would be yes, in all probability. Wallace Matthews, New York Times, "Mets’ Yoenis Cespedes Has Yet Another Injury Setback," 10 June 2018 In all probability, the thing will end Wednesday as the Celtics hunker down at home and close the door. Bob Ford,, "Does T.J. McConnell playoff performance represent changing of the guards for Sixers? | Bob Ford," 8 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'probability.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of probability

15th century, in the meaning defined at sense 1

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Phrases Related to probability

in all probability

Statistics for probability

Last Updated

15 Oct 2018

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Time Traveler for probability

The first known use of probability was in the 15th century

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More Definitions for probability



English Language Learners Definition of probability

: the chance that something will happen

: something that has a chance of happening

: a measure of how often a particular event will happen if something (such as tossing a coin) is done repeatedly


prob·a·bil·i·ty | \ˌprä-bə-ˈbi-lə-tē \
plural probabilities

Kids Definition of probability

1 : the chance of happening The probability of rain is low.

2 : something likely Rain is a probability.

3 : a measure of how likely a given event is The probability of a coin landing face up is ¹/₂.

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Comments on probability

What made you want to look up probability? Please tell us where you read or heard it (including the quote, if possible).


a state of commotion or excitement

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