# Activation function

> A function that enables neural networks to learn nonlinear relationships between features and the label.

A function that enables [neural networks](https://wiki.g15e.com/pages/Artificial%20neural%20network.txt) to learn [nonlinear relationships](https://wiki.g15e.com/pages/Nonlinear%20relationship.txt) between [features](https://wiki.g15e.com/pages/Feature%20(machine%20learning.txt)) and the [label](https://wiki.g15e.com/pages/Label%20(machine%20learning.txt)).

Popular activation functions include:

- [Rectified linear unit](https://wiki.g15e.com/pages/Rectified%20linear%20unit.txt)
- [Sigmoid function](https://wiki.g15e.com/pages/Sigmoid%20function.txt)