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ultraviolet dropout

1. The disappearance of an extremely distant galaxy from a telescope image when viewed through an ultraviolet filter, caused by the absorption of the galaxy's emitted ultraviolet radiation by intergalactic hydrogen gas.

2. A technique that identifies galaxies as extremely distant by comparing images taken through visible light (in which distant objects are often detectable) and ultraviolet filters (in which they are not).

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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Indo-European & Semitic Roots Appendices

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