Momentous is something that is considered very important and is given the prominent importance among all. It gives a paramount importance to the adjective which is being talked about. It is an adjective.
Synonyms of Momentous:
prominent,vital, important, critical, crucial.
Antonyms of Momentous:
trivial, unimportant, non-prominent and trifling.
1) 15th August 1947 is a momentous event in the history of India because that was the day when the Indians got freedom from the clutches of the British.
2)Personally, I consider August 24 as momentous because that was the day when I received the first award of my career.
3)Personal relations and love are more momentous than money in this world.
4)Reducing the tax and giving subsidy to the farmers were momentous decisions by the government, which helped them get back into power in the following general elections.