alteration vs occurrence

alteration and occurrence both are nouns.

Word	Noun	Adjective	Verb	Adverb
alteration	Yes	No	No	No
occurrence	Yes	No	No	No

As nouns, occurrence is a hypernym of alteration; that is, occurrence is a word with a broader meaning than alteration:

alteration: an event that occurs when something passes from one state or phase to another
occurrence: an event that happens

Other hypernyms of alteration include happening, natural event, occurrent.

alteration (noun)	occurrence (noun)
the act of revising or altering (involving reconsideration and modification)	an event that happens
the act of making something different (as e.g. the size of a garment)	an instance of something occurring
an event that occurs when something passes from one state or phase to another