probability

probability — noun

1. the degree to which a particular event or situation is expected to happen, cover

1.nounC1
Definition

the degree to which a particular event or situation is expected to happen, covering both informal judgments of chance and exact mathematical values expressed as fractions or percentages.

Example

There is a high probability of rain this afternoon, so Kian took his umbrella to work.

collocation: high probability of + noun

Scientists calculated the probability that the asteroid would hit Earth as extremely low.

probability that + clause

Common collocations
  • high probability
  • low probability
  • good probability
  • slight probability
  • calculate the probability
  • probability of
  • probability that
Synonyms
  • likelihood

    very similar meaning; likelihood is slightly less formal and less mathematical

  • chance

    more informal; 'chance' often suggests a less precise, more everyday estimate

  • odds

    used especially in betting; 'odds' are usually given as ratios (e.g. 5 to 1), not percentages

Antonyms

Grammar Patterns

probability of + noun/gerund

probability that + clause

Usage Note

This sense covers two related ideas: (a) a general, non-numerical idea of likelihood ('there's a good probability she'll come'), and (b) a precise mathematical value used in statistics, gambling, and science ('the probability of heads is 0.5'). For the mathematical meaning, the value is always expressed as a number between 0 and 1 (or 0% to 100%).

Common Mistakes

There is a big probability of snow.
There is a high probability of snow.
In English, probability is described as 'high/low/good/slight', not 'big/small'.

2. used in the fixed phrase 'the probability is that' to say that something is almo

2.nounC2
Definition

used in the fixed phrase 'the probability is that' to say that something is almost certain to happen or be the case, without giving a precise numerical value.

Example

The probability is that the meeting will be postponed until next Tuesday.

fixed phrase: the probability is that + clause

Given the amount of snow that has fallen, the probability is that schools will be closed.

Common collocations
  • the probability is that
  • probability is that
Synonyms
Antonyms

Grammar Patterns

the probability is that + subject + verb

probability is that + subject + verb

Usage Note

This sense is almost always used with the definite article ('the') in the opening phrase 'the probability is that'. It is a fixed expression used to state a confident prediction. Unlike sense 1, this sense does not take 'of': you do NOT say 'the probability is of rain'.

Common Mistakes

Probability is that it will rain.
The probability is that it will rain.
The definite article 'the' is required in this fixed expression.

3. a specific thing, event, or result that is expected or likely to happen.

3.noun
Definition

a specific thing, event, or result that is expected or likely to happen.

Example

A peace agreement between the two countries is a real probability this year.

countable: a + adjective + probability

With their two best players injured, defeat is a strong probability in the next match.

countable: is a + adjective + probability

Common collocations
  • a probability
  • a strong probability
  • a real probability
  • a distinct probability
  • the most likely probability
Synonyms
  • prospect

    similar meaning but often used in plural ('prospects for peace'); slightly more formal

  • likelihood

    usually uncountable; less natural in 'X is a likelihood'

  • possibility

    wider range; a possibility is less certain than a probability

Antonyms

Grammar Patterns

a probability

strong probability

real probability

Usage Note

This sense is countable — you can say 'a probability' or 'probabilities' (plural). It names a concrete possibility, not just an abstract level of chance. Compare: 'The probability of rain is 80%' (sense 1 — a number) vs. 'Rain is a probability' (sense 3 — a likely event).

Common Mistakes

Rain is probability.
Rain is a probability.
In this countable sense, you need the article 'a'.
Idioms

in all probability

idiom

used to say that something is very likely to happen or is almost certainly true, based on the available evidence.

The committee will, in all probability, announce the decision before the weekend.

The missing cat has, in all probability, been taken in by a neighbor.

(on) the balance of evidence/probability

idiom

Considering all the available information to decide what is most likely true.

On the balance of evidence, the fire started in the kitchen.

The judge decided on the balance of probability that the contract was valid.

(on) the balance of probability/evidence

idiom

Considering all the available information to decide what is most likely true.

On the balance of probability, the missing cat was taken by a fox.

The committee concluded on the balance of evidence that the policy was effective.

in all probability…

idiom

Used to say that something is very likely to happen or be true.

In all probability, the train will arrive late due to the storm.

She will in all probability accept the job offer from the bank.

Word family

  • probable
    adjectiveB1
  • probably
    adverbA2
  • improbable
    adjectiveB2
  • improbability
    nounC1
  • probabilistic
    adjectiveC2
  • probability density
    nounC2

Synonym discussion

Sense: noun/1

Probability, likelihood, chance, and odds all relate to how possible something is, but they differ in precision and context. Probability is the most formal and technical term — it is standard in mathematics, science, and statistics ('the probability of a Type I error'). Likelihood is very similar in meaning but slightly less mathematical; it is common in everyday analysis ('there is a strong likelihood that prices will rise'). Chance is the most informal and covers both general possibility ('there's a chance of rain') and numerical estimates ('a 30% chance'). Odds is restricted to betting and ratio-based contexts ('odds of 3 to 1'). In writing, use probability for formal or technical claims, likelihood for reasoned estimates, and chance for casual guesses. For example: 'The probability of a false positive is 5%' (scientific); 'The likelihood of success is low' (general analysis); 'I give it a 50% chance' (informal).

likelihood ↗chance ↗odds ↗

Common collocations

Nouns

Adverbs

Phrases

  • in all probability
  • the probability is that
  • probability of occurrence
  • probability and statistics

Prepositions

Etymology

LatinFrenchEnglish

The word 'probability' comes from Latin 'probabilitas', meaning 'worthiness of approval, credibility'. This came from 'probabilis' ('worthy of approval, provable'), which in turn came from 'probare' ('to test, to prove, to judge worthy'). The word entered English in the 1400s through French 'probabilité', initially carrying the sense of 'trustworthiness' or 'credibility'. By the 1600s, as mathematical probability theory developed (especially through the work of Pascal, Fermat, and later Laplace), the meaning shifted from 'something worthy of belief' to the modern sense of a numerical measure of likelihood.