Page "Cartesian coordinate system" Paragraph 89

Each axis may have different units of measurement associated with it ( such as kilograms, seconds, pounds, etc .).

Although four-and higher-dimensional spaces are difficult to visualize, the algebra of Cartesian coordinates can be extended relatively easily to four or more variables, so that certain calculations involving many variables can be done.

( This sort of algebraic extension is what is used to define the geometry of higher-dimensional spaces.

) Conversely, it is often helpful to use the geometry of Cartesian coordinates in two or three dimensions to visualize algebraic relationships between two or three of many non-spatial variables.