vacuum tube vs thermionic tube

vacuum tube and thermionic tube both are nouns.

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

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

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

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

vacuum 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