Whitsuntide vs Whitsun

Whitsuntide and Whitsun both are nouns.

Word	Noun	Adjective	Verb	Adverb
Whitsuntide	Yes	No	No	No
Whitsun	Yes	No	No	No

As nouns, Whitsuntide and Whitsun are synonyms defined as:

Whitsuntide and Whitsun: Christian holiday; the week beginning on Whitsunday (especially the first 3 days)

Other synonyms of Whitsuntide include Whitweek.

Whitsuntide (noun)	Whitsun (noun)
Christian holiday; the week beginning on Whitsunday (especially the first 3 days)	Christian holiday; the week beginning on Whitsunday (especially the first 3 days)