# momentous

/moʊˈmɛntəs/ (US) · /məʊmˈɛntəs/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/momentous
Updated: 2026-05-08

## Definition

very important because it will have a big effect on the future. You use this to describe a major event or decision.

For teachers: of great importance or significance, especially in its bearing on future events. Often used to describe historical turning points or life-changing decisions.

## Examples

- The two countries signed a momentous peace treaty today.
- Graduating from university is a momentous occasion that marks the start of a new chapter in life.
- The discovery of the new vaccine was a momentous achievement that promised to alter the course of global public health for generations to come.

## Pitfalls

- Not "a momentary decision" but "a momentous decision" — Learners confuse 'momentous' (important) with 'momentary' (lasting only a short time).

## Usage notes

- Typically used as an attributive adjective before a noun like 'decision', 'occasion', or 'event'.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.