Cylindrical coordinates are a generalization of two-dimensional polar coordinates to three dimensions by superposing a height (z) axis. Unfortunately, there are a number of different notations used for the other two coordinates. Either r or rho is used to refer to the radial coordinate and either phi or theta to the azimuthal coordinates. Arfken, for instance, uses (rho, phi, z), while Beyer uses (r, theta, z). In this work, the notation (r, theta, z) is used.
The following table summarizes notational conventions used by a number of authors.