migration

the act or an instance of migrating

a group of people, birds, etc, migrating in a body

chem a movement of atoms, ions, or molecules, such as the motion of ions in solution under the influence of electric fields

The seasonal movement of a complete population of animals from one area to another. Migration is usually a response to changes in temperature, food supply, or the amount of daylight, and is often undertaken for the purpose of breeding. Mammals, insects, fish, and birds all migrate. The precise mechanism of navigation during migration is not fully understood, although for birds it is believed that sharp eyesight, sensibility to the Earth's magnetic field, and the positions of the Sun and other stars may play a role.

The movement of one atom or more, or of a double bond, from one position to another within a molecule.

The movement of ions between electrodes during electrolysis.