Can we represent 4D graphically? Actually I know that axes are always perpendicular but after three axes we cannot draw any other axis that is perpendicular to all the other three axes.
can any one say how can we draw another axes which is mutually perpendicular
 A: This cannot be done. Humans can only perceive three dimensions and the axis that you are asking for would imply that we can vision a fourth spatial dimension which cannot be done. However, it is not impossible that there could be other spatial dimensions in a addition to the three we have. We just cannot see or sense them. There are actual theories (like string theory) which studies dimensionality beyond this 3D setup. Such dimensions are said to "compactified". Picture a cylinder in a line extending in the x-direction. Obviously this cylinder has three dimensions. Now consider yourself to be moving far away from this cylinder. At some stage it will appear to be a line or 1-dimensional. In reality, it has more dimensions but they are so small or "compactified" that they are not perceivable.
A: Truth is if you want 4 dimensions that are orthogonal, they do not even need to be spatial. For example you can use color to add an extra dimension. Or another example, you can use time. There are many dimensions that we can see. You can even make extra spatial dimensions using local dimensions techniques. For example if you draw a grid of clocks you can have 2 usual spatial coordinates (column and row number), plus 2 or even 3 angular coordinates (each clock hour, minute, second hands). This kind of creativity is used in visualization techniques.
A: One way of looking at dimensionality is the number of points that can be placed equidistantly, minus one. So you can place two points for a line (1D), three points in an equilateral triangle for 2D, and four points in a tetrahedron for 3D. That is as far as it goes; you can not place five points equidistantly in "our space", so we cannot represent 4D.
