A crescent-shaped portion of a plane or sphere bounded by two arcs of circles.
[Latin lūna, moon; see leuk- in the Appendix of Indo-European roots.]
(click for a larger image)lune
The area of this lune, the outer arc of which is a semicircle centered at M and the inner arc of which is a quarter circle centered at C, is equal to the area of the triangle ABC.
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.