1. The sign √ placed before a quantity, indicating extraction of the root designated by a raised integer. When extracting a square root, the raised integer is customarily omitted.
2. The radical sign together with a horizontal bar extending from its top to the end of the expression from which a root is to be extracted.
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.