a. A large, usually continuous segment of a surface or space: the upper regions of the atmosphere.
b. A portion of the earth's surface distinguished from others by some characteristic: the coastal region; the region of storm damage.
c. A bioregion.
d. A political district or unit, often with its adjacent lands: the Osaka region.
2. An area of the body having natural or arbitrarily assigned boundaries: the abdominal region.
3. An area of interest or activity; a sphere: the region of gender studies.
4. An approximate degree or amount: costs in the region of one billion dollars.
[Middle English, from Old French, from Latin regiō, regiōn-, from regere, to rule; see reg- 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.