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.

---

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 )

---

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.

---

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.

---

probability More Idioms  

1. see in all probability.

---

Other Word Forms

• nonprobability noun
• superprobability noun

Etymology

Origin of probability

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

Example Sentences

“The latest attacks increase the probability of a prolonged disruption scenario, where supply losses could persist even if geopolitical tensions ease, reinforcing upside risks to prices,” wrote ING analysts in a note on Monday.

From Barron's • Mar. 30, 2026

Using a percentage chance of a violation of the rules, launch weather officers use a combination of meteorological and climatological data, local knowledge, and experience to forecast this probability.

From BBC • Mar. 30, 2026

A fundamental and powerful concept in probability is Bayes’s theorem, developed by the 18th-century statistician Thomas Bayes.

From The Wall Street Journal • Mar. 29, 2026

AI models are “probabilistic,” meaning they guess based on probability and don’t provide high enough levels of accuracy.

From MarketWatch • Mar. 27, 2026

“It’s a zero. There is zero probability that your default rate will be five percent.”

From "The Big Short" by Michael Lewis

Related Words

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