\begin{array}{col1col2...coln} column 1 entry & column 2 entry ... & column n entry \\ . . . \end{array}
Math arrays are produced with the array environment. It has a single mandatory argument describing the number of columns and the alignment within them. Each column, coln, is specified by a single letter that tells how items in that row should be formatted.
Column entries must be separated by an &. Column entries may include other LaTeX commands. Each row of the array must be terminated with the string \\.