# Concurrency
## CS Concepts — The Codex Coding
**URL:** https://thecodex.expert/coding/concepts/concurrency/
**Type:** concept | **Confidence:** high | **Last verified:** 2026-06-01

## CANONICAL DEFINITION
Concurrency is the ability of a program to have multiple computations in progress at the same time — interleaving on one CPU core or running in parallel on multiple cores — requiring synchronisation mechanisms to prevent conflicts over shared mutable state.

## REQUIRES
concepts/functions, concepts/scope

## ENABLES
concepts/concurrency-vs-parallelism, concepts/synchronous-vs-asynchronous

## COMMONLY CONFUSED WITH
concurrent != parallel; GIL != thread safety in Python; async/await is not multithreading

## SOURCES
- Java Language Specification §17
- Python GIL docs
- ISO C++11 §29
- Hewitt 1973 Actor model IJCAI

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