Generally speaking, a matrix is a rectangular arrangement of a set of elements or entries such as numbers or symbols that are arranged in rows and columns. The dimensions of the matrix in Figure 1 are three by four (3 × 4), as there are three rows and four columns. When discussing matrices, it is conventional to designate the number of rows as “m” and the number of columns as “n” and refer to the rows before the columns when describing the full size of a matrix. For example, Figure 1 displays a 3 (rows) × 4 (columns) matrix, which designates its full size. This entry describes the way matrices are utilized in social network analysis and defines common terminology such as ways and modes.