gas-discharge tube vs tube

gas-discharge tube and tube both are nouns.

Word	Noun	Adjective	Verb	Adverb
gas-discharge tube	Yes	No	No	No
tube	Yes	No	Yes	No

As nouns, tube is a hypernym of gas-discharge tube; that is, tube is a word with a broader meaning than gas-discharge tube:

gas-discharge tube: a tube in which an electric discharge takes place through a gas
tube: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

Other hypernyms of gas-discharge tube include electron tube, thermionic tube, thermionic vacuum tube, thermionic valve, vacuum tube.

gas-discharge tube (noun)	tube (noun)
a tube in which an electric discharge takes place through a gas	conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases
	an electric railway operating below the surface of the ground (usually in a city)
	electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope
	(anatomy) any hollow cylindrical body structure
	a hollow cylindrical shape

gas-discharge tube (verb)	tube (verb)
	place or enclose in a tube
	convey in a tube
	ride or float on an inflated tube
	provide with a tube or insert a tube into