| array of mn scalars arranged in m rows and n columns|
Note 1 to entry: The scalars in the array are called elements of the matrix.
Note 2 to entry: The matrix notation is also used with scalar quantities instead of scalars, these quantities being not necessarily of the same kind. Examples are the impedance matrix and the H-matrix (see IEC 60027-2). A matrix notation is sometimes used for operators. This should be justified in each case.
Note 3 to entry: A matrix is represented by a letter symbol in italic bold-face type or by the table of elements within parentheses: A or . The notation (Aij) is also used, for example to distinguish the matrix A from a vector A. Square brackets are also used instead of parentheses. For a matrix A, the element at the row i and the column j may be denoted by (A)ij or by Aij if there is no ambiguity.
Note 4 to entry: A matrix is complex if its elements are complex numbers or quantities. A complex matrix may be denoted by A, the elements by (A)ij or (A)ij.