# fair coin

idiom

Source: https://englishreference.com/idiom/fair-coin
Updated: 2026-08-10

## Meaning

A sequence of independent Bernoulli trials (a Bernoulli process) with probability 1/2 of success on each trial.

## Examples

- If you flip a fair coin, you have a fifty percent chance of heads.
- To ensure the game is unbiased, we must use a fair coin for the opening toss.
- Assuming the experiment relies on a fair coin, the theoretical probability of observing ten consecutive heads remains extremely low.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.