ef·fi·ca·cy 
(ĕfĭ-kə-sē)
(ĕfĭ-kə-sē)n.
Power or capacity to produce a desired effect; effectiveness.
[Latin efficācia, from efficāx, efficāc-, efficacious; see EFFICACIOUS.]
- unanimity
- unanimous
- unanimously
- unanimousness
- unannounced
- unanswerability
- unanswerable
- unanswerableness
- unanswerably
- unanticipated
- unanticipatedly
- unapologetic
- unapologetically
- unappealable
- unappealably
- unappealing
- unappealingly
- unappeasable
- unappeasably
- unappetizing
- unappetizingly
- unappreciated
- unappreciative
- unappreciatively
- unapproachability