photocathode vs cathode

photocathode and cathode both are nouns.

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

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

photocathode: a cathode that emits electrons when illuminated
cathode: a negatively charged electrode that is the source of electrons entering an electrical device

photocathode (noun)	cathode (noun)
a cathode that emits electrons when illuminated	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