marriage vs monogamy

marriage and monogamy both are nouns.

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

As nouns, monogamy is a hyponym of marriage; that is, monogamy is a word with a more specific, narrower meaning than marriage:

marriage: the state of being a married couple voluntarily joined for life (or until divorce)
monogamy: the practice or state of having only one spouse at a time

marriage (noun)	monogamy (noun)
the act of marrying; the nuptial ceremony	the practice or state of having only one spouse at a time
two people who are married to each other
the state of being a married couple voluntarily joined for life (or until divorce)
a close and intimate union