langsyne vs lang syne

langsyne and lang syne both are nouns.

Word	Noun	Adjective	Verb	Adverb
langsyne	Yes	No	No	Yes
lang syne	Yes	No	No	Yes

As nouns, langsyne and lang syne are synonyms defined as:

Other synonyms of langsyne include auld langsyne, good old days, old times.

As adverbs, langsyne and lang syne are synonyms defined as:

Other synonyms of langsyne include long ago, long since.

langsyne (noun)	lang syne (noun)
past times remembered with nostalgia	past times remembered with nostalgia

langsyne (adverb)	lang syne (adverb)
of the distant or comparatively distant past	of the distant or comparatively distant past