All,
In ams math, the default behavior of align is to align each equation on the
&. By default, each equation is numbered. Individual equations can be
labeled and referenced. Try:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
F(x)&=\int_0^x f(t)\, dt\label{eq:1}\\
F'(x)&=f(x)\label{eq:2}
\end{align}
In equation~(\eqref{eq:1}) and equation~(\eqref{eq:2}), we see\ldots
\end{document}
To suppress number of equations, we use the align* environment. Try:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\end{align*}
\end{document}
When one wants to number an aligned environment as a group, we use aligned
instead of align. This requires that we be in math mode. Try:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}\label{fundthm}
\begin{aligned}
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\end{aligned}
\end{equation}
\end{document}
I can get this with amsl, with:
\usemodule[amsl]
\starttext
\placeformula[fundthm]
\startalign
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\stopalign
We see in the \in{Fundamental Theorem}[fundthm] \ldots
\stoptext
I'm not sure how to label and reference individual equations in the align
environment, however.