klystron vs thermionic tube

klystron and thermionic tube both are nouns.

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

As nouns, thermionic tube is a hypernym of klystron; that is, thermionic tube is a word with a broader meaning than klystron:

klystron: an electron tube used to generate or amplify electromagnetic radiation in the microwave region by velocity modulation
thermionic tube: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

Other hypernyms of klystron include electron tube, thermionic vacuum tube, thermionic valve, tube, vacuum tube.

klystron (noun)	thermionic tube (noun)
an electron tube used to generate or amplify electromagnetic radiation in the microwave region by velocity modulation	electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope