aquarium vs fish bowl

aquarium and fish bowl both are nouns.

Word	Noun	Adjective	Verb	Adverb
aquarium	Yes	No	No	No
fish bowl	Yes	No	No	No

As nouns, fish bowl is a hyponym of aquarium; that is, fish bowl is a word with a more specific, narrower meaning than aquarium:

aquarium: a tank or pool or bowl filled with water for keeping live fish and underwater animals
fish bowl: a transparent bowl in which small fish are kept

Other hyponyms of aquarium include fishbowl, goldfish bowl.

aquarium (noun)	fish bowl (noun)
a tank or pool or bowl filled with water for keeping live fish and underwater animals	a transparent bowl in which small fish are kept
	a state of affairs in which you have no privacy