prob·​a·​bil·​i·​ty | \ ˌprä-bə-ˈbi-lə-tē How to pronounce probability (audio) \
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

Increases beyond that raise the probability of extreme weather, deadly heat and rising sea levels. Greg Ip, WSJ, "The Unrealistic Economics of the Green New Deal," 13 Feb. 2019 In some cases for which there is a lower probability of fertilization, a process known as intracytoplasmic sperm injection (ICSI) is used. Jennifer Gerson, Marie Claire, "Health & Fitness," 1 Oct. 2018 Insurance regulators require Florida’s private market insurers to have enough surplus and reinsurance capital on hand to pay maximum losses following a storm with a probability of occurring once every 100 years. Ron Hurtibise,, "Finally, a bit of good news about insurance rates: 'Once in a while, Florida gets lucky'," 4 June 2018 The rules of probability cannot bend, and many excellent women candidates lost this year. Brianna Wu, Marie Claire, "I Ran for Congress. I Lost. I'm Persisting. Quitting Is Not an Option In the Trump Era.," 9 Oct. 2018 That increases the attack surface, and increases the probability of software error. Shoshana Wodinsky, The Verge, "Many Android devices ship with firmware vulnerabilities, researchers find," 10 Aug. 2018 According to statistical probability, that would rank Lovell in a high-risk category for a potential host of lifelong behavioral and physical health ailments. John Schmid, Milwaukee Journal Sentinel, "Marquette President Mike Lovell championing new ideas to address core Milwaukee problem: trauma," 5 Mar. 2018 The 2018 Huntsville Mardi Gras Grand Parade set for Saturday Feb. 10th has been canceled due to the probability of heavy rain. Michael Dumas,, "Show Us Your Mardi Gras Gowns: Mystic Stripers celebrate Mardi Gras history," 9 Feb. 2018 China has passed legislation forcing game makers to publish the probability of individual items appearing in loot boxes, while Japan has cracked down on certain forms of prize draws in games. James Vincent, The Verge, "Loot box crackdown forces Final Fantasy and Kingdom Hearts games out of Belgium," 23 Nov. 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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Statistics for probability

Last Updated

16 Apr 2019

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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 How to pronounce probability (audio) \
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).


an enemy or opponent

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