uncertain

uncertain — adjective

1. feeling doubt or hesitation about what to do, believe, or choose, especially whe

1.adjectiveB1
Definition

feeling doubt or hesitation about what to do, believe, or choose, especially when the right decision is not yet clear to you.

Example

Eri was uncertain whether to take the job in Taipei or stay home.

be uncertain whether + to-infinitive

The committee remained uncertain about how to fund the new library in the district.

remain uncertain about + noun phrase

Common collocations
  • uncertain about the outcome
  • uncertain whether to go
  • uncertain of the facts
  • feel uncertain
  • remain uncertain
Synonyms
  • unsure

    more common in everyday speech; less formal than uncertain

  • hesitant

    focuses on the delay or reluctance to act, not just the mental doubt

  • doubtful

    implies a stronger leaning toward one side being unlikely

  • undecided

    specifically about a choice between options, not about beliefs

Antonyms
  • certain

    the direct opposite; having no doubt

  • sure

    more informal and commonly used in everyday conversation

Grammar Patterns

be uncertain about + noun/gerund

be uncertain whether + to-infinitive

feel uncertain of + noun

remain uncertain about + wh-clause

Usage Note

Predicative only — this sense of uncertain never appears directly before a noun. Use “a confused decision” or “a doubtful look” instead of “an uncertain decision” when describing the decision itself.

Common Mistakes

I am uncertain person about the plan.
I am uncertain about the plan.
uncertain in this sense is predicative and cannot modify a noun directly.
She is uncertain to come to the party.
She is uncertain whether to come to the party.
use whether (not to) to express indecision about an action.

2. not yet decided, confirmed, or clearly known — the details, outcome, or facts of

2.adjectiveB1
Definition

not yet decided, confirmed, or clearly known — the details, outcome, or facts of a situation are still open or not firmly established.

Example

The cause of the fire remains uncertain even after months of investigation by experts.

remain uncertain (predicative, subject = fact)

It is still uncertain whether the music festival will go ahead despite the storm damage.

it is uncertain whether + clause

Common collocations
  • uncertain future
  • uncertain outcome
  • uncertain origin
  • remain uncertain
  • it is uncertain whether
Synonyms
  • unclear

    focuses on lack of clarity; more neutral tone

  • vague

    suggests the information itself is imprecise or poorly defined

  • indefinite

    implies no fixed limits or deadlines have been set

  • unresolved

    suggests an issue that remains open and needs to be settled

Antonyms
  • certain

    something that is known or fixed without doubt

  • decided

    a matter or outcome that has been settled

Grammar Patterns

something is uncertain

it is uncertain whether / if / when…

remain uncertain

uncertain + noun (attributive)

Usage Note

Unlike sense 1 (NOT SURE), this sense works both predicatively and attributively. When used before a noun, it describes something whose outcome or nature is unknown: “uncertain future,” “uncertain outcome.” Frequently used in academic and journalistic writing with dummy-it structures.

3. likely to shift or change from one condition to another, especially in ways that

3.adjectiveB2
Definition

likely to shift or change from one condition to another, especially in ways that are hard to predict or depend on.

Example

The weather in this mountain area is uncertain — storms can arrive without any warning.

uncertain weather (attributive describing unpredictable nature)

Otis's job situation has been uncertain ever since the company announced the layoffs last month.

situation / future + be uncertain (predicative)

Common collocations
  • uncertain weather
  • uncertain future
  • uncertain times
  • uncertain income
  • uncertain market
  • uncertain political situation
  • grow uncertain
  • become uncertain
Synonyms
  • unpredictable

    stronger emphasis on not being able to foresee what comes next

  • unstable

    suggests a tendency to change in a negative, disruptive way

  • variable

    more neutral and technical; used for measurable changes like temperature or speed

  • volatile

    stronger and more dramatic; implies sudden, extreme shifts

Antonyms
  • stable

    not changing or likely to change; steady

  • constant

    continuing at the same level or rate without variation

  • reliable

    can be trusted to stay the same or perform dependably

Grammar Patterns

uncertain + noun (attributive)

become / grow uncertain

something is uncertain (predicative, describing changeable nature)

Usage Note

This sense overlaps with “unstable” but is broader — it covers any kind of unpredictable change (weather, prices, moods, political conditions), not just structural instability. When used predicatively, the subject is typically a condition or situation rather than a person.

Common Mistakes

She is uncertain today because of the fight.' (when meaning moody)
Her mood is uncertain today because of stress.
this sense describes a condition, not a person's feelings.
Idioms

in no uncertain terms

idiom

in a direct, forceful, and very clear way — leaving no room for doubt or misunderstanding about what you mean.

The manager told the team in no uncertain terms that late submissions would not be accepted.

Camila told her landlord in no uncertain terms that the broken heating system must be fixed immediately.

Word family

Synonym discussion

Sense: adjective/2

All five words describe a lack of definiteness, but they differ in what kind of definiteness is missing. Uncertain (the broadest term) covers anything whose outcome, identity, or truth is not firmly known: “The date of the trial remains uncertain.” Unclear focuses on the lack of intelligibility — information exists but is hard to interpret: “The instructions were unclear.” Vague implies that the information itself is imprecise or poorly expressed: “His explanation was too vague to follow.” Indefinite suggests that no fixed limit or deadline has been set: “She is on indefinite leave.” Unresolved implies an issue or problem that has not yet been settled: “The dispute remains unresolved after months of negotiation.” Choose uncertain when the core issue is a missing piece of knowledge; choose vague when the issue is imprecision; choose unresolved when closure is expected but hasn’t come.

uncertain ↗unclear ↗vague ↗indefiniteunresolved

Common collocations

Nouns

  • uncertain future
  • uncertain outcome
  • uncertain times
  • uncertain weather
  • uncertain income
  • uncertain origin
  • uncertain situation

Adverbs

  • highly uncertain
  • deeply uncertain
  • increasingly uncertain
  • still uncertain
  • somewhat uncertain

Phrases

Prepositions

  • uncertain about
  • uncertain of
  • uncertain as to

Etymology

LatinFrenchEnglish

Uncertain was formed in English around the 1300s by adding the prefix un- (meaning “not”) to the adjective certain, which came from Old French certain (“fixed, settled, sure”). Certain itself traces back to the Latin word certus (“determined, resolved, sure”), the past participle of cernere (“to decide, to separate, to sift”). So at its root, uncertain literally means “not decided” or “not sifted out.”