# Bac

CEFR C1 · Noun

Source: https://englishreference.com/word/bac
Updated: 2026-08-15

## Definition

the amount of alcohol in a person's blood. It is a number used by doctors and police to see if someone is too drunk to drive safely.

For teachers: the concentration of alcohol in the bloodstream, expressed as a percentage or mass per volume. Often used in legal and medical contexts to determine levels of intoxication.

## Examples

- The driver had a high BAC after the party.
- Police officers use breathalyzer tests to measure a driver's BAC during routine traffic stops.
- Legal limits for BAC vary by country, but even a small amount of alcohol can significantly impair the motor skills and reaction times necessary for operating a motor vehicle.

## Usage notes

- Typically used as an acronym for 'blood alcohol concentration'; often appears with the definite article 'the' or as a bare noun in technical reports.

---

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.