Whitsunday vs Pentecost

Whitsunday and Pentecost both are nouns.

Word	Noun	Adjective	Verb	Adverb
Whitsunday	Yes	No	No	No
Pentecost	Yes	No	No	No

As nouns, Whitsunday and Pentecost are synonyms defined as:

Whitsunday and Pentecost: seventh Sunday after Easter; commemorates the emanation of the Holy Spirit to the Apostles; a quarter day in Scotland

Whitsunday (noun)	Pentecost (noun)
seventh Sunday after Easter; commemorates the emanation of the Holy Spirit to the Apostles; a quarter day in Scotland	seventh Sunday after Easter; commemorates the emanation of the Holy Spirit to the Apostles; a quarter day in Scotland
	(Judaism) Jewish holy day celebrated on the sixth of Sivan to celebrate Moses receiving the Ten Commandments