tr.v. sub·tend·ed, sub·tend·ing, sub·tends
1. Mathematics To be opposite to and delimit: The side of a triangle subtends the opposite angle.
2. To underlie so as to enclose or surround: flowers subtended by leafy bracts.
[Latin subtendere, to extend underneath : sub-, sub- + tendere, to extend; see ten- 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.