lending library vs circulating library

lending library and circulating library both are nouns.

Word	Noun	Adjective	Verb	Adverb
lending library	Yes	No	No	No
circulating library	Yes	No	No	No

As nouns, lending library and circulating library are synonyms defined as:

lending library and circulating library: library that provides books for use outside the building

lending library (noun)	circulating library (noun)
library that provides books for use outside the building	library that provides books for use outside the building