I have made a number of alterations, some of them rather subtle, to the text and style elements on the Puzzle of the Day page that don't normally change. How many changes can you spot?

1. "16 is better than 17, because 17 is worse than 16" is an example of what kind of flawed reasoning?
2. "I'm so tired I could sleep for a hundred years" is an example of what rhetorical device, which is exaggeration taken to the extreme?
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3. What's another word for "exceedingly concise"? It's closely related to a punctuation symbol that indicates the omission of words.
4. The answers to the questions above relate to three items in a traditional set of four. What I have left out?

Solution

1. Circular (reasoning)
2. Hyperbole
3. Elliptical
4. The missing conic section is the parabola. I wondered if "parabolic" had any meaning outside math, and it turns out it does: it's the (uncommon) adjectival form of "parable", as in the Parables of Jesus.

It's pretty clear why circular reasoning is called that, but why do the others have double meanings in math and rhetoric/logic? Ellipse, parabola, and hyperbola are from the Greek for "to fall short", "to throw beside", and "to throw beyond". The mathematical sense comes from the slope at which a plane has to hit a cone to make each kind of section:

I'll let you imagine how the rhetorical senses might have arisen.

Congratulations to yesterday's winners Atticus, Ena, Jacob C., Andrew H., Peter M., Mr. Gregg, Kate, Graham, and Jason. Thanks to everybody who made a guess!