1. The vertebrate spine or spinal column.
2. Something, such as the keel of a ship, that resembles a backbone.
3. The main support or major sustaining factor: the backbone of a thesis.
4. Strength of character; determination: displayed grit and backbone in facing adversity.
a. A ridge forming the principal axis of a mountain.
b. The principal mountain ridge, range, or system of a region.
6. Chemistry The main chain of atoms in a polymer.
7. Computers A high-speed communications line that connects smaller, local networks to each other, especially in a wide area network.
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.