1. A unit of area in the US Customary System, used in land and sea floor measurement and equal to 160 square rods, 4,840 square yards, or 43,560 square feet. See Table at measurement.
a. acres Property in the form of land; estate.
b. Archaic A field or plot of arable land.
3. often acres A wide expanse, as of land or other matter: "acres of textureless carpeting" (Anne Tyler).
[Middle English aker, field, acre, from Old English æcer; see agro- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.