This is difficult to visualize, as we can only perceive the world around us as a three-dimensional space, and even more challenging to measure. An example of a four-dimensional object is the ...

They discern one another's shape both by touching and by seeing ... the square conceives the possibility of a fourth dimension. He even goes so far as to suggest that there may be no limit to ...

We live in a three-dimensional reality. Because of that, it’s pretty hard to imagine what a four-dimensional reality might be like, but that isn’t stopping physicists from trying to figure it out.