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 $\left(\begin{array}{ccc}{A}_{11}& \cdots & A_{1n}\\ ⋮& \ddots & ⋮\\ A_{m1}& \cdots & A_{mn}\end{array}\right)$. The notation (A_ij) 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 A_ij 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.