An electrode is an electrical conductor that is used to make contact with a non-metallic part of a circuit, such as a semiconductor, an electrolyte, a vacuum, or air. Electrodes are essential components of electrochemical cells, where reduction and oxidation reactions take place at the electrodes. The electrode at which reduction takes place is called the cathode, while oxidation takes place at the anode. Electrodes are classified as either active or inert, depending on whether or not they participate in the oxidation-reduction reaction. An active electrode is one that actively participates in the electrochemical cells chemical reaction, while an inert electrode is chemically unreactive and is only present so that current can flow through the electrochemical cell.

An electrode is a point where the current enters and leaves the electrolyte/Electrochemistry/Electrodes/Standard_Hydrogen_Electrode). When the current leaves the electrode, it is known as the cathode, and when the current enters, it is known as the anode/Electrochemistry/Electrodes/Standard_Hydrogen_Electrode). Electrodes are usually made of metals, but they need not be metals. Some commonly used materials for electrodes in analytical chemistry are amorphous carbon, gold, and platinum. Glass electrodes are often used in pH measurements, where the glass is chemically doped to be selective to hydrogen ions.

Electrodes have many uses, including generating electrical current and passing it through non-metal objects to alter them in several ways. They are also used to measure conductivity, in different battery types, electroplating and electrolysis, welding, cathodic protection, membrane electrode assembly, for chemical analysis, and Taser electroshock weapon. In the medical field, electrodes are used in ECG, ECT, EEG, and defibrillator, and for electrophysiology techniques in biomedical research.