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ray 1 (rā)
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n.
1.
a. A narrow stream of radiant energy, especially visible light, traveling in a straight or nearly straight line.
b. A narrow stream of particles such as protons traveling in a straight or nearly straight line.
c. A rapidly moving particle traveling in a straight or nearly straight line.
d. rays Sunshine: Let's go to the beach and catch some rays.
2. A small amount; a trace: not a ray of hope left.
3. Mathematics A straight line extending from a point. Also called half-line.
4. A structure or part having the form of a straight line extending from a point, such as:
a. Any of the bright streaks that are seen radiating from some craters on the moon.
b. A ray flower or the strap-shaped portion of the corolla of a ray flower.
c. A branch of an umbel.
d. One of the bony spines supporting the membrane of a fish's fin.
e. One of the arms of a starfish or other radiate animal.
tr.v. rayed, ray·ing, rays
1. To send out as rays; emit.
2. To supply with rays or radiating lines.
3. To cast rays on; irradiate.

[Middle English rai, from Old French, from Latin radius, pointed stick, spoke, radius of a circle, ray of light (from the representation of rays of light as spearlike shafts), of unknown origin.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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:

    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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