caustic soda vs hydrated oxide

caustic soda and hydrated oxide both are nouns.

Word	Noun	Adjective	Verb	Adverb
caustic soda	Yes	No	No	No
hydrated oxide	Yes	No	No	No

As nouns, hydrated oxide is a hypernym of caustic soda; that is, hydrated oxide 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
hydrated oxide: a compound of an oxide with water

Other hypernyms of caustic soda include hydroxide, lye.

caustic soda (noun)	hydrated oxide (noun)
a strongly alkaline caustic used in manufacturing soap and paper and aluminum and various sodium compounds	a compound of an oxide with water