cold cathode vs cathode

cold cathode and cathode both are nouns.

Word	Noun	Adjective	Verb	Adverb
cold cathode	Yes	No	No	No
cathode	Yes	No	No	No

As nouns, cathode is a hypernym of cold cathode; that is, cathode is a word with a broader meaning than cold cathode:

cold cathode: a cathode that is a source of electrons without being heated
cathode: a negatively charged electrode that is the source of electrons entering an electrical device

cold cathode (noun)	cathode (noun)
a cathode that is a source of electrons without being heated	a negatively charged electrode that is the source of electrons entering an electrical device
	the positively charged terminal of a voltaic cell or storage battery that supplies current