# Which one should I use: \begin{align} or \begin{aligned}?

Which one should I use: \begin{align} or \begin{aligned}?

• You use align outside the math mode, and aligned inside the math mode. Jan 12, 2011 at 9:16
• @KennyTM: Only that? Jan 12, 2011 at 9:17
• I don't study amsmath in detail, but that's the only difference I perceive. I could be wrong though :) Jan 12, 2011 at 9:19
• …: Answers can be found in the »amsmath« manual or in the »Math mode« document. Jan 12, 2011 at 9:20
– hola
Apr 17, 2019 at 13:13

If you have a series of equations that you want to have mutual alignment, then you would use align. If the equations are part of a larger equation, then aligned is the right environment.

I often will use \begin{equation}\begin{aligned} ... \end{aligned}\end{equation} to give a single equation number to a group, for example if I'm showing steps.

align is used for entering to math-mode while aligned is used for multiple horizon alignment. For example

 \begin{align}
\begin{aligned}
2x+3 &= 7 & 2x+3-3 &= 7-3 \\
2x &= 4 & \frac{2x}2 &= \frac42\\
x &= 2
\end{aligned}
\end{align}


ps. the example is adapted from Math Mode document of Herbert Voß.

For grouping the multiple lines equation, you should use gather or multline.

You can use align inside subequation to get the numbering (1a) and (1b). Then you can refer the the equation system with (1) and to the subequations directly.

\begin{subequations}
\begin{align}
a &= b \\
c &= d
\end{align}
\end{subequations}