"Zero dimension. In science, we think it's a point without any direction to speak of. It's the smallest unit we can understand dimensions." Zhao Guofeng tapped a black spot on the whiteboard. Then, he drew a straight line on the black spot. "Countless zero-dimensional spaces form one dimension. It's formed by countless zero-dimensional points, which also gives it the only meaning of length and direction."
Then, Zhao Guofeng drew many long lines beside this long line, forming a black rectangle. "Two-dimensional space is this side. Imagine, a one-dimensional straight line only has one direction. In fact, we all know that there are countless such directions. If we want to, we can connect any two zero-dimensional points and we can get any straight line and direction. The space formed by all straight lines is called a plane, or two-dimensional. Two-dimensional space has length and width."