redundancy vs repetitiousness

redundancy and repetitiousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
redundancy	Yes	No	No	No
repetitiousness	Yes	No	No	No

As nouns, repetitiousness is a hypernym of redundancy; that is, repetitiousness is a word with a broader meaning than redundancy:

redundancy: repetition of messages to reduce the probability of errors in transmission
repetitiousness: verboseness resulting from excessive repetitions

Other hypernyms of redundancy include repetitiveness.

redundancy (noun)	repetitiousness (noun)
repetition of an act needlessly	verboseness resulting from excessive repetitions
the attribute of being superfluous and unneeded
(electronics) a system design that duplicates components to provide alternatives in case one component fails
repetition of messages to reduce the probability of errors in transmission