unstable
/ʌnˈsteɪ.bəl/adjective, verb
unstable is spelled U-N-S-T-A-B-L-E: 8 letters and 3 syllables. It appears 7.4 times per million words in written English, the 8,669th most frequent word form (wordfreq, 2021 data). As an adjective, unstable means “Not stable” (English Wiktionary, September 2026).
How many letters and syllables are in unstable?
| Letters | 8: U-N-S-T-A-B-L-E |
|---|---|
| Syllables | 3 (from its American pronunciation) |
| In writing | 7.4 times per million words; the 8,669th most frequent word form |
| Wrong spellings searched | none measured in search |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How common is unstable?
Unstable appears 7.4 times per million words in written English, the 8,669th most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce unstable?
- /ʌnˈsteɪ.bəl/
Unstable has 3 syllables (counted from its American pronunciation in the CMU Pronouncing Dictionary).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: LL-Q1860_(eng)-Vealhurl-unstable.wav, Wikimedia Commons (author and licence on each file's page).
Forms of unstable
- more unstable comparative
- most unstable superlative
- unstables present, singular, he/she/it
- unstabling participle, present
- unstabled participle, past
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does unstable mean?
The meanings the English Wiktionary records, quoted as written there (source below).
adjective
- 1
Not stable.
unstable foundation
- 2
Having a strong tendency to change.
- 3
Fluctuating; not constant.
politically unstable
- 4
Fickle.
- 5
Unpredictable.
- 6
Readily decomposable.
chemically unstable
- 7
Radioactive, especially with a short half-life.
verb
- 1
To release (an animal) from a stable.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Unstable in Spanish, French, German and Portuguese
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does unstable come from?
From Middle English unstable; equivalent to un- (not) + stable.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).