nuclear reactor vs moderator

nuclear reactor and moderator both are nouns.

Word	Noun	Adjective	Verb	Adverb
nuclear reactor	Yes	No	No	No
moderator	Yes	No	No	No

nuclear reactor (noun)	moderator (noun)
(physics) any of several kinds of apparatus that maintain and control a nuclear reaction for the production of energy or artificial elements	someone who mediates disputes and attempts to avoid violence
	someone who presides over a forum or debate
	in the Presbyterian church, the officer who presides over a synod or general assembly
	any substance used to slow down neutrons in nuclear reactors