card catalogue vs card index

card catalogue and card index both are nouns.

Word	Noun	Adjective	Verb	Adverb
card catalogue	Yes	No	No	No
card index	Yes	No	No	No

As nouns, card catalogue and card index are synonyms defined as:

card catalogue and card index: an alphabetical listing of items (e.g., books in a library) with a separate card for each item

Other synonyms of card catalogue include card catalog.

card catalogue (noun)	card index (noun)
an alphabetical listing of items (e.g., books in a library) with a separate card for each item	an alphabetical listing of items (e.g., books in a library) with a separate card for each item
a library catalog in which each publication is described on a separate file card