Abscissa and ordinate is the distance between the projection and the origin of the axis, and whose sign is given by the location on the projection relative to the origin (before: negative; after: positive). Usually these are the horizontal and vertical coordinates of a point in a two-dimensional rectangular Cartesian coordinate system. The terms can also refer to the horizontal and vertical axes respectively (typically "x"-axis and "y"–axis) of a two-dimensional graph. An ordered pair consists of two terms—the abscissa (horizontal, usually "x") and the ordinate (vertical, usually "y")—which define the location of a point in two-dimensional rectangular space. Though the word "abscissa"
Spectral abscissa the left half plane, i.e. formula_3 Spectral radius Spectral abscissa In mathematics, the spectral abscissa of a matrix or a bounded linear operator is the supremum among the real part of the elements in its spectrum, sometimes denoted as formula_1 Let λ, ..., λ be the (real or complex) eigenvalues of a matrix "A" ∈ C. Then its spectral abscissa is defined as: For example, if the set of eigenvalues were = {1+3i,2+3i,4-2i}, then the Spectral abscissa in this case would be 4. It is often used as a measure of stability in control theory, where a continuous system is