string bass vs contrabass

string bass and contrabass both are nouns.

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

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

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

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

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

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