probability

American  

[prob-uh-bil-i-tee] / ˌprɒb əˈbɪl ɪ ti /

noun

plural

probabilities

1. the quality or fact of being probable.

2. a strong likelihood or chance of something.

   The probability of the book's success makes us optimistic.

3. a probable event, circumstance, etc..

   Our going to China is a probability.

4. Statistics.

   1. the relative possibility that an event will occur, as expressed by the ratio of the number of actual occurrences to the total number of possible occurrences.

   2. the relative frequency with which an event occurs or is likely to occur.

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idioms

1. in all probability, very probably; quite likely.

   The factory will in all probability be relocated.

probability British  

/ ˌprɒbəˈbɪlɪtɪ /

noun

1. the condition of being probable

2. an event or other thing that is probable

3. statistics a measure or estimate of the degree of confidence one may have in the occurrence of an event, measured on a scale from zero (impossibility) to one (certainty). It may be defined as the proportion of favourable outcomes to the total number of possibilities if these are indifferent ( mathematical probability ), or the proportion observed in a sample ( empirical probability ), or the limit of this as the sample size tends to infinity ( relative frequency ), or by more subjective criteria ( subjective probability )

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probability Scientific  

/ prŏb′ə-bĭl′ĭ-tē /

1. A number expressing the likelihood of the occurrence of a given event, especially a fraction expressing how many times the event will happen in a given number of tests or experiments. For example, when rolling a six-sided die, the probability of rolling a particular side is 1 in 6, or 1/6.

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probability Cultural  

1. A number between zero and one that shows how likely a certain event is. Usually, probability is expressed as a ratio: the number of experimental results that would produce the event divided by the number of experimental results considered possible. Thus, the probability of drawing the ten of clubs from an ordinary deck of cards is one in fifty-two (1:52), or one fifty-second.

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probability More Idioms  

1. see in all probability.

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Other Word Forms

• nonprobability
  noun
• superprobability
  noun

Etymology

Origin of probability

From the Latin word probābilitās, dating back to 1545–55. See probable, -ity

Explanation

Probability has to do with how likely something is to happen. If there's a 50/50 chance, then the probability is 50%. Probability is a part of math involving percentages and chance. The probability of a thing happening is the same as the odds or chances of something happening. When you watch a weather forecast, it might say there's a 30% chance of showers; that's probability. Gambling — on sports or something else — is also based on probability. Since most things in life are uncertain, it's helpful to know if the probability is high or low for things you want to do or try.

Example Sentences

Probability was integral to David Marr’s understanding of brain function.

From The Wall Street Journal • Mar. 29, 2026

In a later set of messages, Epstein initially expressed doubt about the woman’s interest in Summers before changing his tune, writing that “she is never ever going to find another Larry summers. Probability ZERO.”

From Slate • Nov. 24, 2025

AEP or "Annual Exceedance Probability" is used to express the likelihood of a flood occurring in a given area each year.

From Science Daily • Nov. 19, 2024

Win Probability Shift: This play increased Detroit’s chances of winning by 10.17%.

From Seattle Times • Feb. 9, 2024

Birthdays, Death Days, and ESP Probability theory began with gambling problems in the seventeenth century, and something of the gaming flavor and appeal clings to it to this day.

From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos

Related Words

• anticipation
• chance
• contingency
• expectation
• feasibility
• odds
• possibility
• prospect