# Homotopy Type Theory dependent type (Rev #1)

A dependent type is a family of types indexed by - “depending on” - values of another type.

Given a type $A$ in a universe of types $\mathcal{U}$, a dependent product type (or ‘pi-type’) $B$ is a family of types:

$\Pi_{(a:A)}B(a)$

Similarly, a dependent sum type (or ‘sigma-type’) $B$ is a family of types:

$\Sigma_{(a:A)}B(a)$

Revision on May 9, 2014 at 21:56:20 by Alexis Hazell?. See the history of this page for a list of all contributions to it.