Definition
To deteriorate is to get worse gradually — and usually to keep getting worse. Buildings deteriorate without maintenance, health deteriorates with age, relations deteriorate after an insult. The word implies a process rather than an event: not a collapse but a slide, often one that accelerates once it begins, because each loss makes the next easier. What deteriorates was once in good condition; the word always carries the memory of better days.
Examples
- Without regular maintenance, the bridge deteriorated until it had to be closed.
- Relations between the two countries deteriorated rapidly after the border incident.
- His eyesight began to deteriorate in his late forties.
Synonyms
worsen · decline · decay · degrade · degenerate
In TOEFL & IELTS
An IELTS Writing Task 1 essential: when a line graph slides downward, 'air quality deteriorated steadily' scores higher than 'got worse'. Task 2 problem paragraphs lean on 'deteriorating conditions/standards'. TOEFL listening uses it for ecosystems and patient health. The noun is 'deterioration'; the formal register is exactly what exam writing rewards.