Here's how it works:
* "Moment" is the root word and refers to a point in time or a brief period.
* "-ous" is a common adjective-forming suffix. It transforms the noun "moment" into an adjective, implying that something is full of, characterized by, or relating to moments.
Therefore, "momentous" signifies something that is very important, significant, or of great consequence, implying that the "moment" is weighty or impactful.
This process of understanding word parts and their functions is called morphology. It helps us decipher the meanings of unfamiliar words and understand the nuances of language.