# Definition:Trace (Linear Algebra)/Matrix

## Definition

Let $A = \sqbrk a_n$ be a square matrix of order $n$.

The trace of $A$ is:

$\ds \map \tr A = \sum_{i \mathop = 1}^n a_{ii}$

### Using Einstein Summation Convention

The trace of $A$, using the Einstein summation convention, is:

$\map \tr A = a_{ii}$

## Also see

• Results about traces of matrices can be found here.