# How to have a multiline equation in an array of equations?

I am in the situation where I need to define some parameters similar to each other.
For this reason I would like to define them in an eqnarray or align.
Unfortunately, one of the right hand part of the definitions are overly long for a single line.

Is it possible to use a multline or similar inside an eqnarray or align?

• A general recommendation: Never use eqnarray. The multi-line display math environments -- such as align -- provided by the amsmath package are far super to eqnarray.
– Mico
Aug 19 '19 at 13:36
• If you load mathtools, you can use multlined (within an align since it's an extension of amsmath). Aug 19 '19 at 13:39

Is it possible to use a multline or similar inside an ... align?

You can't use a multline environment inside an align environment. However, it's alright to use aligned and multlined environments -- the latter requires loading the mathtools package -- inside align environments.

A minimum working example (MWE):

\documentclass{article}