memorialisation vs observance

memorialisation and observance both are nouns.

Word	Noun	Adjective	Verb	Adverb
memorialisation	Yes	No	No	No
observance	Yes	No	No	No

As nouns, observance is a hypernym of memorialisation; that is, observance is a word with a broader meaning than memorialisation:

Other hypernyms of memorialisation include ceremonial, ceremonial occasion, ceremony.

memorialisation (noun)	observance (noun)
a ceremony to honor the memory of someone or something	the act of observing; taking a patient look
	conformity with law or custom or practice etc.
	the act of noticing or paying attention
	a formal event performed on a special occasion