# ruinous

/ˈɹuənəs/ (US) · /ɹˈuːɪnəs/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/ruinous
Updated: 2026-10-12

## Definition

causing serious damage or costing so much money that it destroys everything. You use this to describe something that leads to total failure or loss.

For teachers: causing or tending to cause catastrophic destruction or total financial collapse. Often describes costs, effects, or consequences that lead to permanent failure.

## Examples

- The high interest rates had a ruinous effect on the small business.
- The legal battle proved ruinous for the family, eventually forcing them to sell their ancestral home to cover the costs.
- Historians argue that the ruinous taxation policies of the late empire were a primary catalyst for the eventual collapse of central authority.

## Usage notes

- Commonly modifies nouns like 'cost', 'effect', 'impact', or 'debt'.

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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.