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re·frac·tion

(rĭ-frăkshən)

1. The deflection of a wave, such as a light or sound wave, when it passes obliquely from one medium into another having a different index of refraction.

2. Astronomy The apparent change in position of a celestial object caused by the bending of light rays as they enter Earth's atmosphere.

3. Medicine

a. The ability of the eye to bend light so that an image is focused on the retina.

b. Determination of this ability in an eye.

re·fraction·al, re·fractive adj.

re·fractive·ly adv.

re·fractive·ness, re′frac·tivi·ty (rē′frăk-tĭvĭ-tē) n.

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refraction

refraction of light

i: angle of incidence

r: angle of refraction

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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