mediocrity vs ordinariness

mediocrity and ordinariness both are nouns.

Word	Noun	Adjective	Verb	Adverb
mediocrity	Yes	No	No	No
ordinariness	Yes	No	No	No

As nouns, ordinariness is a hypernym of mediocrity; that is, ordinariness is a word with a broader meaning than mediocrity:

mediocrity: ordinariness as a consequence of being average and not outstanding
ordinariness: the quality of being commonplace and ordinary

Other hypernyms of mediocrity include mundaneness, mundanity.

mediocrity (noun)	ordinariness (noun)
ordinariness as a consequence of being average and not outstanding	the quality of being commonplace and ordinary
a person of second-rate ability or value