# nLab 3-morphism

Contents

### Context

#### Higher category theory

higher category theory

# Contents

## Definition

A 3-morphism in an n-category is a morphism between 2-morphisms.

## Examples

For $A$ an abelian group, the 3-fold delooping $\mathbf{B}^3 A$ is a 3-groupoid whose 3-morphisms are given by $A$.

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