Meaning & use
unstable
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Meanings
adjectivecomparable
Not firmly balanced or fixed, and likely to fall, collapse or change.
Grammar: Used before a noun or after a linking verb: an unstable ladder; the ladder is unstable.
Patterns
- unstable structure
The ladder was unstable, so he asked a friend to hold it.
Engineers closed the bridge because the support looked unstable.
The old table is too unstable to hold the lamp.
adjectivecomparable
Likely to change suddenly or to cause trouble, as a country, market or situation.
Grammar: Often describes politics, prices or the economy.
Patterns
- politically unstable
- economically unstable
The region remains politically unstable after the election.
Oil prices have been unstable all year.
An unstable economy makes people nervous about spending.
adjectivecomparable
Having moods or behavior that change quickly and unpredictably.
Grammar: Used for people, often with emotionally or mentally.
Patterns
- emotionally unstable
- mentally unstable
The witness seemed emotionally unstable after the accident.
Her unstable mood made it hard to plan anything.
Doctors worried that the patient was mentally unstable.
adjectivecomparablechemistrytechnical
Likely to break down or react easily, as a chemical compound.
Grammar: Used in chemistry and physics: an unstable compound.
Patterns
- unstable compound
- unstable isotope
Nitroglycerin is a highly unstable compound.
The unstable isotope decays into a different element.
Scientists stored the unstable substance at very low temperatures.
Word forms
| comparative | more unstable |
|---|---|
| superlative | most unstable |
Common combinations
- politically unstable
- Investors avoid countries that are politically unstable.
- emotionally unstable
- He became emotionally unstable after the loss.
- unstable ground
- The house was built on unstable ground.
- highly unstable
- The chemical is highly unstable when heated.
- unstable situation
- The unstable situation worried the diplomats.
Synonyms and how they differ
- shaky
- Shaky is more informal and suggests weakness or trembling, as in a shaky table or shaky economy.
- volatile
- Volatile suggests a tendency to change quickly or explode, which is stronger than unstable.
- precarious
- Precarious stresses danger of falling or failing, so it feels more urgent than unstable.
- unsteady
- Unsteady mostly describes movement or balance of people and objects, not countries or compounds.
Opposites
Word family
- stable adjective
- firmly fixed or not likely to change
- instability noun
- the state of being unstable
- stability noun
- the quality of being steady
- destabilize verb
- to make something unstable
- unstably adverb
- in an unsteady way
Commonly confused: unstable or unsettled?
unstable vs unsettled
Unsettled means troubled or changing, as in unsettled weather, but it does not suggest something may collapse.
Practice
The government fell twice in a year, so the country is described as ___.
Choose one answer.
Unstable is the standard word for a country likely to change or fail. Unsteady normally describes balance or movement.
Make it your own
Write a sentence using “unstable”, then check it and compare it with the examples above.