1. The measure of the flow of some quantity per unit area per unit of time.
2. Any substance that will promote the melting of another substance to which it is added.
3. An excessive discharge of fluid.
4. A resin or similar substance that is used in soldering, welding, or brazing in order to remove oxides from the surfaces to be joined and so promote their bonding.
5. In electromagnetism, the electric or magnetic field lines of force that traverse, or through, a given cross-sectional area.
6. Etymology: from Old French flux, which came from Latin fluxus, past participle of fluere, "to flow".

Originally it referred to "excessive flow" (of blood or excrement); an early name for "dysentery"; and then the sense of "continuous succession of changes" is first recorded in 1625.

1. A flow, flowing, or discharge of liquid.
2. The act of flowing and the matter that flows.