In essence, the fourth dimension is an additional axis that can represent measurement mathematically. For dimension, Professor Stephen Hawking, a famous British physicist, has this explanation: it is like a hair, which is a one-dimensional line from a distance. Under the magnifying glass, it is really three-dimensional; If we face time and space, if we have a magnifying glass with high magnification, we should also be able to reveal other possible 4-and 5-dimensional spaces, up to 1 1 dimensional space.

So dimension refers to a perspective, not a fixed number; Judging, explaining, evaluating and determining a thing is a multi-faceted, multi-angle and multi-level condition and concept.

Mathematics is an abstract subject, that is, it uses abstract expressions to explain fundamental things. Now you ask the meaning of four dimensions in mathematics, and I think it is the same as the three-dimensional coordinate system proposed by Descartes.