1. Acting or producing effectively with a minimum of waste, expense, or unnecessary effort: an efficient builder; an efficient factory.
2. Acting directly to produce an effect: the efficient cause of the revolution.
3. Causing less waste or requiring less effort than comparable devices or methods. Used in combination: energy-efficient wind turbines; cost-efficient health care.
[Middle English, from Old French, from Latin efficiēns, efficient-, present participle of efficere, to effect; see EFFECT.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.