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rille also rill

(ril)

1. A long, narrow, roughly straight channel or groove on the surface of a solar system body like a planet or moon.

2. Variant ofrill.

[GermanRille; see rei- in the Appendix of Indo-European roots, fromLow Germanrille; see rei- in the Appendix of Indo-European roots.]

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rille

Ariadaeus, a lunar rille, photographed in 1969 by the crew of Apollo 10

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:

Indo-European Roots

Semitic Roots

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.

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