Контекст. If u r orgaizing a closet, concentrate on doing it with excellence. If u r talking on the phone with a friend, give this friend ur undivided attention. If u r watching a TV-show or movie, enjoy it without doing anything else. Don't kid yourself into believing that it's more efficient to do 2 things at once. There is a difference between EFFICIENCY and EFFECTIVENESS.

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synonyms EFFECTIVE, EFFECTUAL, EFFICIENT, EFFICACIOUS mean producing or capable of producing a result.
EFFECTIVE stresses the actual production of or the power to produce an effect "an effective rebuttal".
EFFECTUAL suggests the accomplishment of a desired result especially as viewed after the fact "the measures to stop the pilfering proved effectual".
EFFICIENT suggests an acting or a potential for action or use in such a way as to avoid loss or waste of energy in effecting, producing, or functioning "an efficient small car".
EFFICACIOUS suggests possession of a special quality or virtue that gives effective power "a detergent that is efficacious in removing grease".

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