The quality of being elective or the state of involving choice and selection.
From 'elective' plus the suffix '-ity' (forming abstract nouns). Both '-ity' and '-ness' can form abstract nouns from the same adjective; '-ity' tends to be more Latinate and formal while '-ness' is more native English.
English speakers have choices in how they nominalize adjectives—'electivity,' 'electiveness,' 'electiveness,' 'election.' We naturally picked the shortest and oldest forms ('election' from Latin) and abandoned the others. Languages are lazy in the best way!
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