# What am I? 'Tis the season of mutual puzzling

I'm born when one is over the treasure spot,
I'm used when you drive to buy a present,
I'm born in the spirit of mutual gift-giving,
Yet I'm literally a super negative one.

Kinda short, so might be open to interpretation, but I assure you your efforts in solving this riddle will be reciprocated with a +1 from me!

• Excellent riddle! And since tensions are running so high on this site, I should explain that 'lynch mob!' is a compliment between riddlers and not a threat :-) – Rand al'Thor Dec 23 '14 at 12:27
• And congrats on making it to the Hot Network Questions :-) – Rand al'Thor Dec 23 '14 at 14:15
• Why is d'alar'cop giving away so much of his reputation as bounties? – Joe Z. Mar 6 '15 at 3:37

reciprocal.

I'm born when one is over the treasure spot,

X marks the spot; "the treasure spot" means X. So "one is over the treasure spot" means 1 over x, or $\frac{1}{x}$, the reciprocal function.

I'm used when you drive to buy a present,

The internal combustion engine, present in the car you drive in, is a type of reciprocating engine.

I'm born in the spirit of mutual gift-giving,

Yet I'm literally a super negative one.

Another notation for the reciprocal of a number is to raise that number to the power of minus one; reciprocals can be denoted by $^{-1}$, "negative one" in superscript.

And finally...

"Your efforts in solving this riddle will be reciprocated with a +1 from me!"

LYNCH MOB! :-)

If you'd like to know how I solved this, the first line always seemed to me the most tractable. I struggled with 'one' and 'X' for a while before eventually thinking of the correct interpretation, which fitted with the third line. As I was writing the answer, I realised how it fitted the fourth line too, and that was when I was certain I was right. The second line was the hardest, and required a quick search on the internet.

Soon it'll be time to post my seasonal riddle...

• Search piston engine in wikipedia! – McMagister Dec 23 '14 at 12:29
• @McMagister - Finished now! Feedback also added :-) – Rand al'Thor Dec 23 '14 at 12:33
• Oh man I would never have got this (didn't know a combustion engine was "<that word>", for a start). So glad I cheated. – Lightness Races in Orbit Dec 23 '14 at 14:15
• @LightnessRacesinOrbit Neither did I when I found the solution! :-) It was the first line that enabled me to crack it; I had to do a bit of Googling for the second line. – Rand al'Thor Dec 23 '14 at 14:17