chemical reactor vs apparatus

chemical reactor and apparatus both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemical reactor	Yes	No	No	No
apparatus	Yes	No	No	No

As nouns, apparatus is a hypernym of chemical reactor; that is, apparatus is a word with a broader meaning than chemical reactor:

chemical reactor: an apparatus for holding substances that are undergoing a chemical reaction
apparatus: equipment designed to serve a specific function

Other hypernyms of chemical reactor include setup.

chemical reactor (noun)	apparatus (noun)
an apparatus for holding substances that are undergoing a chemical reaction	equipment designed to serve a specific function
	(anatomy) a group of body parts that work together to perform a given function