caustic soda vs hydroxide

caustic soda and hydroxide both are nouns.

Word	Noun	Adjective	Verb	Adverb
caustic soda	Yes	No	No	No
hydroxide	Yes	No	No	No

As nouns, hydroxide is a hypernym of caustic soda; that is, hydroxide is a word with a broader meaning than caustic soda:

caustic soda: a strongly alkaline caustic used in manufacturing soap and paper and aluminum and various sodium compounds
hydroxide: a compound of an oxide with water

Other hypernyms of caustic soda include hydrated oxide, lye.

caustic soda (noun)	hydroxide (noun)
a strongly alkaline caustic used in manufacturing soap and paper and aluminum and various sodium compounds	a compound of an oxide with water
	a chemical compound containing the hydroxyl group