Vacuum Tube

cathode ray tube that emits electron rays

In electronics, a vacuum tube, electron tube (inside North America), thermionic valve, or just valve (elsewhere); is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space, often not tubular in form. Many devices called vacuum tubes are filled with low-pressure gas: these are so-called soft valves (or tubes); as distinct from the hard vacuum type, which have the internal gas pressure reduced as far as possible. Almost all depend on the thermal emission of electrons, hence thermionic.
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Noun
1. electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope
(synonym) tube, thermionic vacuum tube, thermionic tube, electron tube, thermionic valve
(hypernym) electronic device
(hyponym) acorn tube
(part-holonym) circuit, electrical circuit, electric circuit
(part-meronym) anode

electron tube

a tube contaning a low pressure gas and two or more metal plates that control the flow of electrons.