du·al (dəl, dy-)
1. Composed of two usually like or complementary parts; double: dual controls for pilot and copilot; a car with dual exhaust pipes.
2. Having a double character or purpose: a belief in the dual nature of reality.
3. Grammar Of, relating to, or being a number category that indicates two persons or things, as in Greek, Sanskrit, and Old English.
1. The dual number.
2. An inflected form of a noun, adjective, pronoun, or verb used with two items or people.
[Latin duālis, from duo, two; see dwo- in the Appendix of Indo-European roots.]
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.