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"
Graph homomorphism can be solved by brute-force in time |"V"("H")|, so polynomial in the size of the input graph "H". In other words, the problem is trivially in P for graphs "G" of bounded size. The interesting question is then what other properties of "G", beside size, make polynomial algorithms possible. The crucial property turns out to be treewidth, a measure of how tree-like the graph is. For a graph "G" of treewidth at most "k" and a graph "H", the homomorphism problem can be solved in time |"V"("H")| with a standard dynamic programming approach. In fact, it is enough to assume