That colorful arc you sometimes see in the sky right after it stops raining? That's a rainbow.
The scientific explanation for a rainbow's appearance is that light is refracted in water droplets, briefly revealing the full visible spectrum of light — all of the colors that make it up. While there are actually about a hundred colors in the visible spectrum, we tend to describe a rainbow as having six or seven. In Old English, there were two words for this phenomenon: scurboga, or "shower-bow," proved to be less popular than renboga, "rain bow."