Difference between Unable and Failed

UNABLE vs FAILED: ADJECTIVE

(usually followed by `to') lacking necessary physical or mental ability
Not able; lacking a certain ability.
Not able; not having sufficient strength, means, knowledge, skill, or the like; impotent; weak; helpless; incapable; -- now usually followed by an infinitive or an adverbial phrase.
Not susceptible to action or treatment.
Lacking mental or physical capability or efficiency; incompetent.
Lacking the necessary power, authority, or means; not able; incapable.
Lacking in power or forcefulness
(usually followed by `to') not having the necessary means or skill or know-how

Helpless, Incapacitated, Unfit, Unsuccessful, Not, Insufficient, Powerless, Impossible, Failed, Able, Not able, Ineffectual, Incapable, Ineffective, Impotent

Fizzled, Faltered, Thwarted, Botched, Foundered, Managed, Lacked, Bungled, Did, Inability, Refused, Attempted, Failure, Unable, Unsuccessful

Helpless, Incapacitated, Unfit, Unsuccessful, Not, Insufficient, Powerless, Impossible, Failed, Able, Not able, Ineffectual, Incapable, Ineffective, Impotent

Missed, Aborted, Rejected, Fizzled, Faltered, Thwarted, Botched, Foundered, Managed, Bungled, Inability, Attempted, Failure, Unable, Unsuccessful

Funds check or reservation was attempted, but failed.
Before bankruptcy, the debtor failed to pay rent.
If my mission president thinks that I have failed than my home stake president and bishop will think that I failed.
The defendants negligently failed to diagnose a placental abruption and failed to recognize the existence of a bleeding condition known as DIC.
Respondent failed to update name and address; failed to notify Secretary of State of criminal charges and conviction.
Current Employer____________________ Have you ever failed a nursing course or failed nursing at another college or nursing school?
Failed to reconfirm at least one drug and failed to reconfirm the adulterant.
God spoke concerning you has failed; all have been fulfilled for you, not one of them has failed.
Either failed to read, or failed to write.
Failed attempts should be logged, unless such action results in the display of the failed password.