a. Joining two nonadjacent vertices of a polygon.
b. Joining two vertices of a polyhedron not in the same face.
2. Having a slanted or oblique direction.
3. Having oblique lines or markings.
4. Relating to or being the front left and back right feet or the front right and back left feet of a quadruped.
1. Mathematics A diagonal line or plane.
2. Something, such as a row, course, or part, that is arranged obliquely.
3. A fabric woven with diagonal lines.
4. A virgule.
[Latindiagōnālis, fromGreekdiagōnios, from angle to angle : dia-, dia- + gōniā, angle, corner; see genu-1 in the Appendix of Indo-European roots.]
(click for a larger image)diagonal
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.