{align} is an environment provided by math packages that permits multiple related equations to be aligned at a common reference point, usually a sign of relation. For general questions about aligning document elements, use {horizontal-alignment} or {vertical-alignment} instead.
The align environment is provided by packages such as amsmath and mathtools. The alignment reference point is indicated by &, which should be placed just before the sign of relation or operation in order to obtain proper spacing. The end of all lines except the last is indicated by \\. The related environment alignat allows horizontal
space between equations on the same line to be explicitly specified. Both align and alignat produce equation numbers on each line; numbers can be omitted from individual lines with \notag or \nonumber. Starred versions without numbering are
provided as well.
The sub-environments aligned and alignedat are building blocks to be used when the
aligned component is only part of a longer multi-line structure. The width of each
component is only as large as necessary, so that it can, for example, be set within
delimiters.
Use of these environments is described in the amsmath users guide, which on a TeX Live
system can be accessed by texdoc amsmath.
For general questions about aligning document elements, use horizontal-alignment or vertical-alignment instead.
