The term cathode, from the Greek words hodos meaning way and kata meaning down, was used by experimenters in the late 19th and early 20th century to designate the conducting material from which negatively charged particles, electrons, emanated when they subjected partially evacuated tubes to high voltage. The tubes were made of glass and typically had a voltage source connected to two pieces of conducting material sealed into the glass and separated by a few inches. The piece of conducting material from which the electrons emanated was called the cathode and the one to which they were attracted was called the anode.

Electrochemical cells consist of one half-cell in which oxidation occurs and a second half-cell in which reduction occurs. Electrons flow though a conductor connecting the two half-cells. At the two ends of the conductor are the electrodes which gather and disperse the electrons. These electrodes are...