monogamousness vs monogamy

monogamousness and monogamy both are nouns.

Word	Noun	Adjective	Verb	Adverb
monogamousness	Yes	No	No	No
monogamy	Yes	No	No	No

As nouns, monogamousness and monogamy are synonyms defined as:

monogamousness and monogamy: the practice or state of having only one spouse at a time

monogamousness (noun)	monogamy (noun)
the practice or state of having only one spouse at a time	the practice or state of having only one spouse at a time