observance vs nuptials

observance and nuptials both are nouns.

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

As nouns, nuptials is a hyponym of observance; that is, nuptials is a word with a more specific, narrower meaning than observance:

observance (noun)	nuptials (noun)
the act of observing; taking a patient look	the social event at which the ceremony of marriage is performed
conformity with law or custom or practice etc.
the act of noticing or paying attention
a formal event performed on a special occasion