What the difference between “orbital” and “orbit”?

Question

What's the difference between "ortibal" and "orbit"? Which one should be used in physics? In quantum mechanics, is "atomic orbital" or "atomic orbit" used? And what about in classical mechanics? A particle's orbit or orbital?

Answer 1

An orbit is a closed trajectory of a classical dynamical system. Properties of orbits or related to orbits are referred to as orbital properties.
http://en.wikipedia.org/wiki/Orbit_(dynamics)

An orbital is a single-electron wave function for an atom or molecule in the Hartree-Fock approximation. (There are also hybrid orbitals for electron pairs in a chemical bond.)
http://en.wikipedia.org/wiki/Molecular_orbital

Thus a particle has an orbit (and related properties such as orbital speed) if it is treated classically (e.g., a planet). But if treated by quantum mechanics (e.g., an electron), it instead has orbitals.

Answer 2

In quantum mechanics, strictly speaking, it's usually "orbital" (http://www.chemguide.co.uk/atoms/properties/orbitsorbitals.html ), in classical mechanics, it's "orbit". But classical mechanics is not very good for atoms.