Unable (adjective)

1. Not able : lacking the power, skill, means, or opportunity.
2. Incapable of being done, performed, or effected.

Origin:

Middle english, from un- + able able, from old english ǣl able, from the root of āgan to possess, have.

Examples:

1. He was unable to walk after the accident.
2. The company is unable to pay its bills.
3. He was unable to find a job.
4. They were unable to reach a decision.
5. The doctor said that the surgery was unable to be performed.