unpredictable

unpredictable — adjective

1. changing so often or so suddenly that you can never guess what will come next

1.adjectiveB2
Definition

changing so often or so suddenly that you can never guess what will come next

Example

The mountain weather near Daichi's village is so unpredictable that storms arrive without warning.

so + adj + that clause for result

Tunde's boss is highly unpredictable, and staff never know what tasks will appear on their desks.

highly + adj for degree

Common collocations
  • highly unpredictable
  • totally unpredictable
  • completely unpredictable
  • unpredictable weather
  • unpredictable behaviour
  • unpredictable outcome
  • unpredictable person
  • unpredictable nature
  • become unpredictable
  • remain unpredictable
Synonyms
  • erratic

    emphasises irregular, inconsistent movement or behaviour; narrower than unpredictable, usually for patterns that jump around

  • volatile

    suggests strong, dangerous, or explosive changes, often in markets, situations, or emotions; more intense than unpredictable

  • fickle

    used mainly for people or weather that change loyalties or conditions frequently; carries a tone of annoyance or disappointment

  • capricious

    suggests sudden changes driven by whim or mood rather than by reason; formal register

Antonyms
  • predictable

    direct opposite — easy to know or guess in advance

  • reliable

    can be trusted to behave or perform in the same way each time

  • steady

    not changing or fluctuating; constant in behaviour, level, or speed

Grammar Patterns

unpredictable + noun

be/seem/become + unpredictable

intensifier + unpredictable (highly/totally unpredictable)

Usage Note

Attributive use (an unpredictable outcome) and predicative use (the outcome is unpredictable) are both common. Frequently modified by intensifiers such as highly, totally, completely.

Common Mistakes

The dice roll was unpredictable because I did not know the number.
The dice roll was random, not unpredictable
the chance of each number is known.' — 'unpredictable' implies no reliable pattern at all, while 'random' refers to a known probability with no single outcome guaranteed.
She is a very unpredictable driver — she always drives at the same speed.
She is a very predictable driver
she always drives at the same speed.' — 'unpredictable' means the opposite of 'always the same.'

Word family

Synonym discussion

Sense: adjective/1

All four words describe things that change in ways that are hard to predict, but they differ in scope and tone. Unpredictable is the broadest and most neutral term — it covers weather, people, outcomes, and machines without judgement. Erratic focuses on irregular movement or performance, often suggesting inconsistency as a flaw: an erratic driver suddenly speeds up and slows down. Volatile implies explosive or dangerous change, common in financial or emotional contexts — a volatile market can crash without warning. Fickle is used for people or forces like weather that switch loyalties or conditions frequently, often carrying a hint of frustration: a fickle friend cancels plans at the last minute. Capricious is the most formal and suggests change driven by whim: a capricious ruler makes laws on a mood. For everyday use, unpredictable works in nearly every situation where one of the others fits.

erraticvolatileficklecapricious

Common collocations

Nouns

Adverbs

Phrases

  • an unpredictable + noun
  • prove unpredictable
  • remain unpredictable
  • become unpredictable

Etymology

LatinFrenchEnglish

Formed in English by adding the negative prefix un- to predictable, which itself comes from predict (to say before) plus the suffix -able (capable of being). Predict traces back through Latin praedicere — prae- (before) plus dicere (to say). The word thus describes something that cannot be spoken of or known in advance.