---
title: "Mass-Energy Equivalence — AP Physics 2 Definition & Guide"
description: "Mass-energy equivalence (E=mc²) means mass is a form of energy. It explains why fission and fusion release energy and connects to conservation of energy."
canonical: "https://fiveable.me/ap-physics-2-revised/key-terms/mass-energy-equivalence"
type: "key-term"
subject: "AP Physics 2"
---

# Mass-Energy Equivalence — AP Physics 2 Definition & Guide

## Definition

Mass-energy equivalence is the concept that mass and energy are interchangeable, as described by Einstein's famous equation E=mc². It states that a small amount of mass can be converted into a large amount of energy, and vice versa.

## Related Study Guides

- [2022 AP Physics 2 Exam Guide](/ap-physics-2-revised/unit-nDdATQV5zgfkYSAz/2022-ap-physics-2-exam-guide/study-guide/7iv6rlD6kfByNtayJzRg)
- [Unit 7 Overview: Quantum, Atomic, and Nuclear Physics](/ap-physics-2-revised/unit-QUWmBhy0eEwkfCSU/review/study-guide/rcA6NJTYu2BTlTMRS2dT)

## Review

### Related Terms

- [Nuclear Fusion](/ap-physics-2-revised/key-terms/nuclear-fusion): The process in which two atomic nuclei combine to form a heavier nucleus, releasing an enormous amount of energy.
- [Nuclear Fission](/ap-physics-2-revised/key-terms/nuclear-fission): The splitting of an atomic nucleus into two smaller nuclei, accompanied by the release of a significant amount of energy.
- [Conservation of Energy](/ap-physics-2-revised/key-terms/conservation-of-energy): The principle stating that energy cannot be created or destroyed but only transferred or transformed from one form to another.