klystron vs thermionic valve

klystron and thermionic valve both are nouns.

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

As nouns, thermionic valve is a hypernym of klystron; that is, thermionic valve 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 valve: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

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

klystron (noun)	thermionic valve (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