doubtful

/ˈdaʊtfl/ (bre, ipa) · /ˈdaʊtfl/ (ame, ipa) · /ˈdau̇t-fəl/ (ame, mw)

doubtful — adjective

  • doubtfulpositive
  • more doubtfulcomparative
  • most doubtfulsuperlative

1. feeling uncertain or lacking confidence about something because you do not have

1.形容詞B1
釋義

feeling uncertain or lacking confidence about something because you do not have enough information or a clear opinion about it

例句

Talia was doubtful about accepting the job because she knew little about the company.

doubtful about + gerund

The doctors felt doubtful whether the new drug would help patients with a rare condition.

felt doubtful whether + clause

同義詞
  • uncertain

    The broadest term; covers any lack of certainty without the questioning tone of doubtful

  • unsure

    Focuses on a person's lack of confidence in their own judgement or knowledge

  • skeptical

    Stronger than doubtful; implies a tendency to disbelieve or demand proof

  • hesitant

    Describes reluctance to act, which may stem from doubt but is not the same as mental uncertainty

反義詞
  • certain

    Having complete confidence or knowledge

  • confident

    Feeling sure about one's own ability or judgement

  • convinced

    Having been persuaded to accept something as true

文法句型

be doubtful about + noun/gerund

be doubtful whether/if + clause

be doubtful that + clause

用法筆記

Subject is usually a person. The uncertainty concerns a specific matter (introduced by about, whether, if, or that), not a general state of mind. Common with linking verbs such as feel, look, seem, and remain.

常見錯誤

❌I am doubtful to join the trip.
✅I am doubtful about joining the trip.
💡'doubtful' takes 'about' before a gerund, not a to-infinitive.
❌She is doubtful for the exam results.
✅She is doubtful about the exam results.
💡Use 'about', not 'for', to introduce the topic of uncertainty.

2. not likely to happen, succeed, or be true; uncertain in outcome or result

2.形容詞B2
釋義

not likely to happen, succeed, or be true; uncertain in outcome or result

例句

The outcome of the election remained doubtful until the very last votes were counted.

outcome remained doubtful

It is doubtful whether the old bridge can survive another harsh winter without major repairs.

It is doubtful whether + clause

同義詞
  • unlikely

    More direct and common; focuses purely on probability without the uncertainty nuance

  • improbable

    Slightly more formal and suggests a lower probability than unlikely

  • questionable

    Carries a judgement of quality or validity rather than pure probability

  • uncertain

    Broader term; can describe any situation with an unknown outcome

反義詞
  • likely

    Having a high probability of happening

  • certain

    Definite; known to be true or to happen

  • assured

    Guaranteed or confidently expected to happen

文法句型

It is doubtful whether + clause

It is doubtful that + clause

Subject + looks/remains/seems doubtful

用法筆記

The subject is a situation, outcome, plan, or possibility — NOT a person. Frequently appears in the impersonal construction 'it is doubtful whether/that + clause' to express a low probability. Compare with sense 1, where the subject is a person feeling uncertain.

常見錯誤

❌I am doubtful that it will rain.' (when referring to the weather)
✅It is doubtful that it will rain.
💡Use the impersonal 'it' construction when the subject is the situation, not a person.
❌The game's success is doubtable.
✅The game's success is doubtful.
💡'Doubtful' is the standard adjective; 'doubtable' is very rare and not used in natural English.