unable

unable — adjective

1. when someone is unable to do something, they cannot achieve it because they lack

1.形容詞A2
釋義

when someone is unable to do something, they cannot achieve it because they lack the necessary ability, time, or opportunity

例句

Minh was unable to attend the meeting because his flight was delayed.

be unable + to-infinitive (reason clause)

The hospital was unable to admit more patients after the power failure.

institutional subject with be unable

同義詞
  • can't

    informal equivalent; used in everyday speech instead of 'unable'

  • incapable

    stronger than 'unable'; suggests a permanent or fundamental lack of ability rather than a temporary one

  • powerless

    focuses on lack of authority or control rather than lack of skill

反義詞
  • able

    direct opposite; can be used before a noun (an able teacher) or with to-infinitive (able to help)

  • capable

    similar to 'able'; usually followed by 'of' (capable of doing)

文法句型

be unable + to-infinitive

feel unable + to-infinitive

remain unable + to-infinitive

用法筆記

Unlike most adjectives, 'unable' cannot be placed before a noun (❌ an unable person). It must always be followed by a to-infinitive clause. In casual conversation, 'can't' is far more common than 'unable'; use 'unable' mainly in formal writing or when you want to sound polite and serious.

常見錯誤

❌I am unable going to the party.
✅I am unable to go to the party.
💡'unable' must be followed by 'to + infinitive', not a gerund.
❌He is an unable student.
✅He is unable to pass the exam.
💡'unable' cannot go before a noun; use 'not a capable' or restructure the sentence.