n. pl. ef·fi·cien·cies
a. The quality or property of being efficient.
b. The degree to which this quality is exercised: The program was implemented with great efficiency and speed.
a. The ratio of the effective or useful output to the total input in any system.
b. The ratio of the energy delivered by a machine to the energy supplied for its operation.
3. An efficiency apartment.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.