This tag involves questions on various coordinate systems. The usual Cartesian coordinate system can be quite difficult to use in certain situations. Some of the most common situations when Cartesian coordinates are difficult to employ involve those in which circular, cylindrical, or spherical symmetry is present. For these situations it is often more convenient to use a different coordinate system.

In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space.

Coordinates systems are often used to specify the position of a point, but they may also be used to specify the position of more complex figures such as lines, planes, circles or spheres. Most coordinate systems use two numbers, a **coordinate**, to identify the location of a point. Each of these numbers indicates the distance between the point and some fixed reference point, called the **origin**.

A coordinate system consists of four basic elements:

$(1)$ Choice of origin

$(2)$ Choice of axes

$(3)$ Choice of positive direction for each axis

$(4)$ Choice of unit vectors for each axis

**Some well-known coordinate system:**

- Cartesian coordinate system
- Polar coordinate system
- Spherical coordinate system
- Cylindrical coordinate system

There are also some other common coordinate systems, for more details you please find https://en.wikipedia.org/wiki/Coordinate_system