The position of a point is given by two numbers, called co-ordinates which refer to the distances of the point from these two axes. By convention the first number, the x-co-ordinate (or abscissa), always indicates the distance from the y-axis and the second number, the y-coordinate (or ordinate) indicates the distance from the x-axis.
Co-ordinates of a point are written as an ordered pair i.e., (x co-ordinate, y co-ordinate). For example, the co-ordinates of the points A and B are (3, 2) and (-2, -4) respectively.
The distance of the point A(3, 2) from the y-axis is 3 units and from the x-axis is 2 units.
In general, co-ordinates of a point P(x, y) imply that distance of P from the y-axis is x units and its distance from the x-axis is y units.
The co-ordinates of the origin O are (0, 0).
The y co-ordinate of every point on the x-axis is 0 and the x co-ordinate of every point on the y-axis is 0. In general, co-ordinates of any point on the x-axis to the right of the origin is (a, 0) and that to left of the origin is (-a, 0), where a is a non-zero positive number.
Similarly, y co-ordinates of any point on the y-axis above and below the x-axis would be (0, b) and (0, -b) respectively where b is a non-zero positive number.
The position of points (x, y) and (y, x) in the rectangular, coordinate system is not the same.
The co-ordinates of all points in the first quadrant are of the type (+, +). Any point in the II quadrant has x co-ordinate negative and y co-ordinate positive (-, +).
Similarly, in III quadrant, a point has both x and y co-ordinates negative (-, -) and in IV quadrant, a point has x co-ordinate positive and y co-ordinate negative (+, -).