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Difference between Effective, Effectual, Efficacious and Efficient

Effective means impressive, in effect, or producing a result.

  • The band put on an effective performance at Saratoga.
  • The new fiscal calendar is effective as of next month.
  • The talks were effective in gaining peace within a few days.

Effectual, like effective, means sufficient to produce a desired effect or result.

  • “Effectual steps for the suppression of the rebellion.”—Macaulay

Efficacious means having the power to achieve the desired effect.

  • The doctor discovered an efficacious remedy for the ailment.

Efficient means achieving results from a good use of resources.

  • Some fuel-efficient cars can get 60 miles to a gallon of gas.