lustrum vs ceremony

lustrum and ceremony both are nouns.

Word	Noun	Adjective	Verb	Adverb
lustrum	Yes	No	No	No
ceremony	Yes	No	No	No

As nouns, ceremony is a hypernym of lustrum; that is, ceremony is a word with a broader meaning than lustrum:

lustrum: a ceremonial purification of the Roman population every five years following the census
ceremony: the proper or conventional behavior on some solemn occasion

lustrum (noun)	ceremony (noun)
a ceremonial purification of the Roman population every five years following the census	the proper or conventional behavior on some solemn occasion
a period lasting five years	any activity that is performed in an especially solemn elaborate or formal way
	a formal event performed on a special occasion