thermionic valve vs electron tube

thermionic valve and electron tube both are nouns.

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

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

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

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

thermionic valve (noun)	electron 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