contrabass vs string bass

contrabass and string bass both are nouns.

Word	Noun	Adjective	Verb	Adverb
contrabass	Yes	Yes	No	No
string bass	Yes	No	No	No

As nouns, contrabass and string bass are synonyms defined as:

contrabass and string bass: largest and lowest member of the violin family

Other synonyms of contrabass include bass fiddle, bass viol, bull fiddle, double bass.

contrabass (noun)	string bass (noun)
largest and lowest member of the violin family	largest and lowest member of the violin family

contrabass (adjective)	string bass (adjective)
pitched an octave below normal bass instrumental or vocal range