probability

UK: /ˌprɒbəˈbɪlɪti/ US: /ˌprɑbəˈbɪlɪti/ ,(prob′ə bil′i tē)

Inflections of 'probability' (n): npl: probabilities

WordReference Random House Learner's Dictionary of American English © 2025

prob•a•bil•i•ty /ˌprɑbəˈbɪlɪti/   n., pl. -ties. 

1. the quality or fact of being probable:
   [uncountable] little probability of success.
2. a probable event, circumstance, etc.:
   [countable] It's a real probability that he'll be reelected.
3. Statistics the possibility or chance that an event will occur, expressed by the number of occurrences that actually happen divided by the total number of possible occurrences:
   [countable] a probability of fifty percent for the coin to land heads up.
   [uncountable] a math problem in probability.

Idioms

4. Idioms in all probability, very probably;
   quite likely:
   The factory will in all probability be shut down by next year.

See -prob-.

WordReference Random House Unabridged Dictionary of American English © 2025

prob•a•bil•i•ty  (prob′ə bil′i tē), n., pl. -ties. 

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
   • 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.
   • the relative frequency with which an event occurs or is likely to occur.
5. Idioms in all probability, very probably;
   quite likely:
   The factory will in all probability be relocated.

• Latin probābilitās. See probable, -ity
• 1545–55

Collins Concise English Dictionary © HarperCollins Publishers::

probability / ˌprɒbəˈbɪlɪtɪ/ noun ( -ties)

1. the condition of being probable
2. an event or other thing that is probable
3. 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)