List of coordinate charts
This article attempts to conveniently list articles on some of the most useful coordinate charts in some of the most useful examples of Riemannian manifolds. The notion of a coordinate chart is fundamental to various notions of a "manifold" which are used in mathematics. In order of increasing "level of structure:" For our purposes, the key feature of the last two examples is that we have defined a metric tensor which we can use to integrate along a curve, such as a geodesic curve. The key difference between Riemannian metrics and semi-Riemannian metrics is that  the former arise from bundling positive-definite quadratic forms, whereas the latter arise from bundling indefinite quadratic forms. A four-dimensional semi-Riemannian manifold is often called a Lorentzian manifold, because these provide the mathematical setting for metric theories of gravitation such as general relativity. For many topics in applied mathematics, mathematical physics, and engineering, it is important to be able to write the most important partial differential equations of mathematical physics (as well as variants of this basic triad) in various coordinate systems which are "adapted" to any symmetries which may be present. While this may be how many  students first encounter a non-Cartesian coordinate chart, such as the cylindrical chart on E (three-dimensional Euclidean space), it turns out that these charts are useful for many other purposes, such as writing down interesting vector fields, congruences of curves, or frame fields in a convenient way. Listing commonly encountered coordinate charts unavoidably involves some real and apparent overlap, for at least two reasons: Therefore, seemingly any attempt to organize them into a list involves multiple overlaps, which we have accepted in this list in order to be able to offer a convenient if messy reference. We emphasize that  this list is far from exhaustive. Favorite surfaces. Here are some charts which (with appropriate metric tensors) can be used in the stated classes of Riemannian and semi-Riemannian surfaces: Here are some charts on some of the most useful Riemannian surfaces (note that there is some overlap, since many charts of S have closely analogous charts on H; in such cases, both are discussed in the same article): Favorite semi-Riemannian surface: "Note:" the difference between these two surfaces is in a sense merely a matter of convention, according to whether we consider either the cyclic or the non -cyclic coordinate to be timelike; in higher dimensions the distinction is less trivial. Favorite Riemannian three-manifolds. Here are some charts which (with appropriate metric tensors) can be used in the stated classes of three-dimensional Riemannian manifolds: ("Note:" not every three manifold admits an isothermal chart.) Here are some charts which can be used on some of the most useful Riemannian three-manifolds: Omitted examples. There are of course many important and interesting examples of Riemannian and semi-Riemannian manifolds which are not even mentioned here, including: In addition, one can certainly consider coordinate charts on complex manifolds, perhaps  with metrics which arise from bundling Hermitian forms. Indeed, this natural generalization is just the tip of iceberg. However, these generalizations are best dealt with in more specialized lists.