Canticle of Canticles vs Song of Songs

Canticle of Canticles and Song of Songs both are nouns.

Word	Noun	Adjective	Verb	Adverb
Canticle of Canticles	Yes	No	No	No
Song of Songs	Yes	No	No	No

As nouns, Canticle of Canticles and Song of Songs are synonyms defined as:

Canticle of Canticles and Song of Songs: an Old Testament book consisting of a collection of love poems traditionally attributed to Solomon but actually written much later

Other synonyms of Canticle of Canticles include Canticles, Song of Solomon.

Canticle of Canticles (noun)	Song of Songs (noun)
an Old Testament book consisting of a collection of love poems traditionally attributed to Solomon but actually written much later	an Old Testament book consisting of a collection of love poems traditionally attributed to Solomon but actually written much later