1. A solid electric conductor through which an electric current enters or leaves an electrolytic cell or other medium.
2. A collector or emitter of electric charge or of electric-charge carriers, as in a semiconducting device.
3. A conducting element that performs one or more of the functions of emitting, collecting, or controlling the movements of electrons or ions in an electron tube, or the movements of electrons or holes in a semiconductor device.
4. A medium for conducting an electrical current from the body to physiological monitoring equipment.
5. A terminal or surface at which electricity passes from one material or medium to another, as at the electrodes of a battery or electrolytic capacitor.
6. One of the terminals of metal, salts, or electrolytes through which electricity is applied to, or taken from, the body or an electric device or instrument.
7. An electronically conductive structure that provides for an electrochemical reaction through the change of oxidation state of a substance.

It may contain or support the reactant or act as the site for the reaction. The anode and cathode of an electric cell are electrodes.

A conductor which is small and which produces stimulation in a concentrated area or to record from a localized section: An electrode is used to make contact with a nonmetallic part of a circuit; such as, a semiconductor or an electrolyte.

An electrode which has the two terminals attached together and near each other.

1. An electrode that develops a standard electric potential.

The calomel electrode is used as a standard in determining the pH (potential of hydrogen) of fluids which refers to a measure of acidity or alkalinity in which the pH of pure water is 7, with lower numbers indicating acidity and higher numbers indicating alkalinity.

2. An electrode consisting of mercury surrounded by a suspension of calomel (a colorless, white or brown tasteless compound, used as a fungicide or insecticide; formerly, as a purgative for purging the bowels; especially, as a laxative in a solution of potassium chloride of a specified strength.

The calomel electrode gives a highly reproducible potential, and is used as a standard, often as a half cell with a glass electrode for determining pH, or with a platinum electrode for establishing redox (oxidation-reduction) potentials or any chemical reactions in which electrons are transferred.

1. A blood-gas electrode that is used to measure the carbon dioxide level of arterial blood.
2. A glass electrode in a film of bicarbonate solution covered by a thin plastic membrane permeable to carbon dioxide but impermeable to water and electrolytes which is normally used to analyze arterial blood samples.

In electrocardiography, an electrode in which connections from three limbs; for example, right arm, left arm, and left leg, are joined and led to the electrocardiograph to form the indifferent electrode, theoretically at zero potential for the system.

A chemical sensor in some clinical laboratory analyzers that functions similarly to a pH electrode.

A recording electrode consisting of an insulated metal wire inside a hollow stainless steel cannula.

Differences in potential are measured using the needle shaft as a reference and the wire tip as the exploring electrode.

An electrode that is capable of both collecting and giving up chloride ions in neutral or acidic aqueous media, consisting of mercury in contact with mercurous chloride, used as a reference electrode in pH measurements.

An electrode with greater resistance than the part of the human body that is enclosed in the circuit.

1. A electrode placed in the esophagus: An esophageal electrode obtains electrocardiographic records from this region or used for electrical pacemaking.
2. A pill electrode that lodges in the esophagus at the level of the atrium: An esophageal pill electrode obtains electrograms and delivers pacing stimuli.

The electrode that controls the convergence of the electron beam and permits focusing the spot on the screen of a cathode ray tube.