ray 1 
(rā)
(rā)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.]