The following outline is provided as an overview of and topical guide to electrical polarity (also called electric polarity).

Many electrical devices, from power sources to loudspeakers, operate in parallel. For proper operation, the connectors of these devices are usually polarized (either through the use of color-coded cables or plugs where the wires cannot be reversed).

Some electrical components are non-polar and function in the same way regardless of the direction of current through them. For example, properties of a resistor are unaffected if the wires on its terminals are swapped. Many other components, however, require a particular direction of current to operate. For terminals of such polarized electrical devices, the anode/cathode terminology is used, with anode being the connection from which the conventional current (positive charges) is flowing inside the component (thus the mnemonic ACID, anode current into device). Anode/cathode terminology is not directly tied to the electric potential of the terminals. Generally, in a battery anode has a negative potential, while in an electric load − positive. The cathode has the opposite potential:

While a bipolar junction transistor (BJT) can be simplistically thought of as two diodes with a shared terminal (anode for the PNP variety), the transistor polarity is usually expressed based on the prevalence of charge carriers in the parts of the device: N-type for the regions where the charge flow is primarily due to the electrons (free due to the presence of dono dopants), and P-type for the regions where the flow is mostly due to electron holes (available spaces for additional electrons made possible by mixing in the acceptors).

The binary ("polar") nature of electrical phenomena was known for a very long time, its similarities to the magnetic polarity were driving research on electromagnetism, with Ørsted finally succeeding in finding a link between the electricity and magnetism (Oersted's law) in 1820. The use of plus and minus signs for the opposing electrical charges was introduced by Georg Christoph Lichtenberg in the 18th century. The terms positive and negative were introduced by Benjamin Franklin in 1747. Franklin compared electricity to fluid, with positive indicating the excess of it, and negative identifying the deficit. Prior to Franklin, nomenclature varied, for example, du Fay called the positive charge vitreous (as it can be obtained by rubbing glass), and negative resinous (obtained by rubbing amber, resin).

Berzelius, in his early 19th-century work on electrochemistry, used the term electrical polarity to explain the chemical reactions. Per Berzelius, while all atoms possessed both positive and negative polarities (electrochemical dualism, long obsolete), the balance depended on an element (with, for example, oxygen being negative and potassium positive), and the reactions were caused by the electrical attraction between the atoms.

The terms anode and cathode, roughly meaning, respectively, way up and way down in Greek, were introduced by Faraday. Knowing well the Earth's magnetic field stretching North to South and assuming that it was generated by a conventional current, the direction of this current, per Ampère's circuital law, should be East to West. Sun in the East goes up and in the West down, hence the terminology.