electron tube vs thermionic tube

electron tube and thermionic tube both are nouns.

Word	Noun	Adjective	Verb	Adverb
electron tube	Yes	No	No	No
thermionic tube	Yes	No	No	No

As nouns, electron tube and thermionic tube are synonyms defined as:

electron tube and thermionic tube: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

Other synonyms of electron tube include thermionic vacuum tube, thermionic valve, tube, vacuum tube.

electron tube (noun)	thermionic tube (noun)
electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope	electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope