acorn tube vs vacuum tube

acorn tube and vacuum tube both are nouns.

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

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

acorn tube: a small vacuum tube; used at high frequencies
vacuum tube: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

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

acorn tube (noun)	vacuum tube (noun)
a small vacuum tube; used at high frequencies	electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope