A line in the euclidean sense is defined as the shortest distance between two points. It is defined to be in 1 direction only, i.e. infinitely thin but also infinitely long. In the Cartesian coordinate system, it is usually described as an equation in x and y of the form , where m is the slope of the line and b is the y-intercept. Any two points define a line, and given specific one can solve for the line's equation.