This chapter discusses primarily concerned with graphs built around two axes, the x-axis and the y-axis. The chapter provides various sections complement titles follow: Rectangular coordinates, logarithmic-logarithmic coordinates, semi-logarithmic coordinates, methods of plotting data and applications. Rectangular coordinate graph paper is most generally used to represent equations. A logarithmic scale is easily constructed by plotting numbers from one to ten on the ordinate versus the logarithm of the number on the abscissa. The logarithmic scale normally is the ordinate and the arithmetic scale is the abscissa on semi-logarithmic paper. The slope of a line on semi-logarithmic coordinates may be calculated from any two points, but the simplest method is the one used previously in which the slope is the logarithmic difference on one cycle divided by the arithmetic difference of one cycle. The slope is a logarithmic difference divided by an arithmetic difference and in the case may be calculated from the two indicated points.