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

The probability is high over the next few days that a tropical cyclone will form, but the forecast models currently keep the storm off shore. Jennifer Gray, CNN, "The tropics are starting to sizzle with tropical formation likely off the US coast this weekend," 23 Aug. 2019 Less extreme For the UK and Germany, the probabilities are a little less extreme. Scott K. Johnson, Ars Technica, "Another European heatwave, another link to climate change," 3 Aug. 2019 The probability for seeing a wolf was twice as high when a buffer was in place, biologist Bridget Borg found in 2016. Zaz Hollander, Anchorage Daily News, "Looking to see a wolf at Denali? A grassroots bus-driver survey puts the odds at ‘not-quite nonexistent’," 29 July 2019 Real probability is about 2% per yer, or 1/20,000 each day. Wire Service, The Mercury News, "Several earthquakes of 3.5-magnitude or greater shook California this week, but no need to panic. Here’s why," 17 July 2019 Conversely, consuming fish, vegetables, and fruit has been tied to a lower probability of depression. Michelle Stacey, Allure, "The "Food as Medicine" Doctrine Hurts More Than It Helps," 8 Aug. 2019 In all probability, their son was buried by somebody else. Dave Altimari,, "In the chaos of the Hartford circus fire, a 6-year-old boy disappeared; now, 75 years later, his family wants to find out what happened to him," 7 July 2019 Critically endangered These animals are facing a high probability of extinction. Liz Langley, National Geographic, "What is extinction? The answer is complicated.," 29 May 2019 States in that region are designated as N/A for this category due to the extremely low probability of a Category 5 storm affecting these areas. Patrick Sisson, Curbed, "As hurricane season starts, potential for coastal property damage tops $1.6 trillion," 7 June 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

3 Sep 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).


readily or continually undergoing change

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