unable to

/ˌʌnˈeɪ.bəl tuː/

incapable of doing something

She was unable to attend the meeting due to illness.

She couldn't go to the meeting because she was sick.

general

Not having the ability or capacity to do something

The machine was unable to process the request.

The machine couldn't handle the request.

He was unable to finish the project on time.

He couldn't complete the project by the deadline.

Often used to express inability due to physical, mental, or situational constraints.

Collocations

unable to doincapable of performing an actionunable to attendincapable of being presentunable to understandincapable of comprehending

capable of doing something

not having the ability to do something

'Unable to' is more formal than 'can't' or 'couldn't'. Use it in professional or written contexts.

Always follow 'unable to' with a verb in its base form (infinitive).

From 'un-' (not) + 'able' (capable) + 'to' (infinitive marker)

Commonly used in formal and informal contexts to describe lack of ability or capacity.

un-

not

prefix

able

capable

root

infinitive marker

particle

English Dictionary