We humans view the world in three dimensions. The first dimension is length or distance. The second is width or height, and the third is depth.
An object that is two dimensional is flat; it has no depth. An example is a piece of paper. A photograph or a map is a two-dimensional representation of a three-dimensional world. So is a shadow.
Some conjecture that time is the fourth dimension, while others call the fourth dimension "space-time" to reflect how space bends out of three dimensions when gravity gets involved. For an interesting discussion, read Steven Hawking's
A Brief History of Time, which is probably available at your local library.
- They are depth width and length of an object
- Some theories hold that there are 10 dimensions of space and one of time
- A dimension is a concept