The adverb form of the adjective momentous is momentously.
e.g. It was a momentously important event.
Ronald Weasley thinks I'm momentous and appaling.
People consider the day of Martin Luther King Jr's assassination a very momentous day in history.
noun
The base word of "momentous" is "moment."
It will be a momentous day when students stop plagiarizing sentences.
Adverb
The word "momentous" comes from the Latin word "momentum," which means "movement" or "importance." "Momentous" is used to describe something of great significance or importance.
The word "momentous" has three syllables: mo-men-tous.
Yes, thankfully we can use it as an adverb. It is the adverb form of the adjective thankful.
You would have to use one of the adverb forms "thoughtfully" or "thoughtlessly."
(You would have to use the adverb, which is tenderly.) She touched his face tenderly.
The part of speech for this particular word is a noun.