n. pl. um·bras or um·brae (-brē)
1. A dark area, especially the blackest part of a shadow from which all light is cut off.
a. The completely dark central portion of the shadow cast by the earth, moon, or other body during an eclipse.
b. The darkest region of a sunspot.
(click for a larger image)umbra
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.