probability

noun

prob·​a·​bil·​i·​ty ˌprä-bə-ˈbi-lə-tē 

plural probabilities

1

a(1)

: the chance that a given event will occur

(2)

: 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

b

: a branch of mathematics concerned with the study of probabilities

2

: something (such as an event or circumstance) that is probable

3

: the quality or state of being probable

4

: a logical relation between statements such that evidence confirming one confirms the other to some degree

Synonyms of probability

• likelihood

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.

Recent Examples on the Web

Only then assess threats, ideally with a simple probability-and-impact matrix. — Bojan Ilic, Forbes.com, 30 Oct. 2026

Barclays estimates a $2 billion peak annual sales opportunity in HS but assigns the drug only a 50% probability of success, citing an unusual dose-response pattern in mid-stage trials and a history of late-stage trial failures in HS. — Elsa Ohlen, CNBC, 30 Oct. 2026

Scientists in Germany have observed electrons crossing an energy gap in graphene with a probability of up to 100%, revealing how intense electric fields can drive quantum transitions in real time. — Neetika Walter, Interesting Engineering, 29 Oct. 2026

The best chance for widespread rain is Friday night, when probabilities grow to 70% to 90%. — Kansas City Star, 29 Oct. 2026

Word History

First Known Use

15th century, in the meaning defined at sense 3

Phrases Containing probability

• conditional probability
• in all probability
• probability density
• probability density function
• probability distribution
• probability function

Rhymes for probability

• affability
• audibility
• bistability
• capability
• changeability
• contractility
• credibility
• culpability
• disability
• disutility
• durability
• fallibility

Kids Definition

probability

noun

prob·​a·​bil·​i·​ty ˌpräb-ə-ˈbil-ət-ē 

plural probabilities

1

: the quality or state of being probable

2

: something probable

3

a

: a measure of how often a particular event will happen if something which results in any of a number of possible events is done repeatedly

the probability of a coin coming up heads is ½

b

: a branch of mathematics concerned with the study of probabilities