monsoon vs rainfall

monsoon and rainfall both are nouns.

Word	Noun	Adjective	Verb	Adverb
monsoon	Yes	No	No	No
rainfall	Yes	No	No	No

As nouns, rainfall is a hypernym of monsoon; that is, rainfall is a word with a broader meaning than monsoon:

Other hypernyms of monsoon include rain, air current, current of air, wind.

monsoon (noun)	rainfall (noun)
a seasonal wind in southern Asia; blows from the southwest (bringing rain) in summer and from the northeast in winter	water falling in drops from vapor condensed in the atmosphere
any wind that changes direction with the seasons
rainy season in southern Asia when the southwestern monsoon blows, bringing heavy rains