Why are there no words that rhyme with purple, orange or silver? Clement Wood's Rhyming Dictionary confirms that there are no rhymes for orange and silver, and he offers only this for purple: "chirp'll." It is hard to imagine a lamer rhyme. We quickly jotted down the first thing that came to mind:

Horrible birds,

Black, yellow, purple,

If the peck doesn't vex you,

The chirp'll.

One initially suspects that purple, orange and silver have no rhymes because they're the words for colors, and someone a long time ago decided colors were too special to be rhymeable. But orange comes from French, purple from Latin by way of Old English, and silver is original Old English going back to the 5th century A.D. The main reason these words have no rhymes is simply the luck of the draw. It's an anomaly. But it's hardly as anomalous as, say, a person with three nostrils, because rhymes aren't actually that common. Check the dictionary. Victoria Neufeldt, editor in chief of Webster's New World Dictionary, asks, "Is there a rhyme for purpose? Murpose?"

Which brings up a more profound why question: Why isn't "murpose" a word? Why not "milver"?

James Hartman, a University of Kansas professor who specializes in American pronunciation, points out that there are zillions of potential words that are never employed, including simple three-letter consonant-vowel-consonant constructions such as "daf," "zat," "bot" and "lep." These aren't used, nor is "milver" or "murpose," in part because there's not a great crushing need for new words, what with something like 500,000 already available, many doing double and triple duty ("racket" can mean something you hit a tennis ball with, or a loud noise or a criminal enterprise).

More important, he says, is that words tend to grow out of other words. Brand names are an exception. Companies come up with new words and they sometimes become so common that they enter the dictionary. Xerox. Kleenex. (But not, for some reason, Q-Tip.)

"Making up some absolutely new words is one of the less frequent ways we have of creating new meanings," says Hartman. "Extending old words is the more typical way, or we can borrow a word from another language."

This has the great advantage of helping us understand what words mean. If we simply declared that a person who speaks out loud during a movie at a theater is a "milver," there'd be no way to trace the etymology. And eventually the professional etymologists would have to find another career. Why do possums "play possum"? One of our great fears is that we'll write too much about the animal world and the column will gradually degenerate into something that should be called Those Daffy Critters. Nonetheless it is healthy to be in touch with our animal relatives, such as the American opossum, generally called simply "possum" since "opossum" sounds like something sold in a fast-food joint, as in "I'll take the jumbo fries and the bag-o-possum." When attacked, it snaps and snarls, but when it starts to lose the fight it suddenly goes stiff and acts dead. It's as though it goes into a trance. Keep in mind that the opossum does this when already in the mouth of some carnivorous predator. Wouldn't that make the opossum all the more easily eaten? How could natural selection allow such a thing to develop?

Because many predators don't want to eat something that isn't writhing and screaming.

That's the answer we get from Desmond Morris in his new book "Animalwatching." The idea is that, deep within the low-wattage brain of a meat-eater, a warning light flashes when meat doesn't squirm. The meat might be spoiled. Laden with gross bacteria. The question we can't answer in this short space is why human beings don't have the same prejudice. (Waiter: "How would you like that steak?" Customer: "Thrashing and whimpering.") The Mailbag: We have been alerted to a petty dispute that has arisen between two competing infotainment columnists about the correct answer to an intriguing puzzle. We will settle this by providing the final, logical, irrefutable answer.

The puzzle: You're on "Let's Make a Deal." Monty Hall shows you three curtains and says that behind one is a car. Behind the other two are goats. You pick Curtain 1. Before Monty shows you what you picked, he reveals what's behind Curtain 2: Goats. Then he asks whether you want to stick with Curtain 1 or switch to Curtain 3. What do you do?

You probably figure it's 50-50 either way. You're wrong. You should switch.

When you initially select a curtain, you have a 33 percent chance of being right. There's a 67 percent chance the car is behind one of the other curtains. Just because Monty raises one of those curtains doesn't change the initial odds: you still have only a 33 percent chance of being right. But now, there's a 67 percent chance the car is behind the one Monty didn't show you.

We didn't believe it either when we first heard it, and indeed we felt it was a direct attack on our entire world view, our Weltanschauung (a gratuitous German term we use to make the column seem smarter).

The solution -- and confusion -- centers around the formulaic nature of a game show.

Monty, imprisoned by formula, wants to heighten drama. This means he cannot show you what's behind your curtain without first showing you what's behind one of the other curtains. Thus, 67 percent of the time, Monty will be in a bit of a pickle, because the car will be behind one of the two curtains you didn't pick, and the formula forces him to show you which one the car isn't behind. He has to tip his hand.

Since two curtains hide goats, Monty Hall will always, always show you a goat behind one of the other curtains no matter which one you select initially. You should ask yourself: Why should your odds suddenly improve from 33 percent to 50 percent just because Monty shows you goats? And surely you can't expect your initial random choice among three curtains to have a 50 percent chance of being right. If only gambling were so easy!

If there were six curtains, and you picked Curtain 1, and Monty showed you what was behind Curtains 2,3,4 and 6, you would suddenly become extremely suspicious of Curtain 5. It's the same principle.

But you probably still don't buy this. That's why Monty never ran out of cars.