Momentary and momentous look similar, but they describe very different ideas.
Momentary means lasting only a very short time. It refers to duration. If something is momentary, it passes quickly. For example, The confusion was momentary, and she understood the instructions a second later.
Momentous means very important, serious, or far reaching. It refers to significance. If something is momentous, it can have a major effect or mark an important event. For example, The court’s decision was momentous for the entire country.
- Use momentary for something brief.
- Use momentous for something important.
A simple way to remember the difference is this: one is about time, and the other is about importance. A momentary delay lasts seconds. A momentous decision can shape years.