The letter ℘: name and origin? (2017)

One thing I've always struggled with Math is keeping track of symbols I don't know the name of yet.

Googling for "Math squiggle that looks like a cursive P" is not a very elegant or convenient way of learning new symbol names.

I wish every proof or equation came with a little table that gave the English pronunciation and some context for each symbol used.

It would make it a lot easier to look up tutorials & ask questions.

As somebody who spends a fair amount of time studying math heavy material that uses math that I never studied formally, this stuff is the bane of my existence. It's one thing to see a random Greek letter, where at least I very likely know what the character "is" (eg, "rho" or "psi" or whatever) and can at least pronounce it to myself and make a mental note "go back and see what rho stands for in this equation". But exactly like you say "squiggle that looks like a cursive P" doesn't easily admit a mental placeholder, AND it's hard to look up later to find out exactly what it is. I've really wanted to tear my last hair out over this a few times. And I am pretty sure one recent such occasion involved this exact character, so this really hits home!

And never mind that cognitive load that comes from managing the use of symbols that are the "same symbol" modulo something the typeface. Trying to read something like

"Little b equals Fraktur Bold Capital B divided by (q times Cursive Capital B) all over Gothic Italic B", blah, blah... then throw in the "weird little squiggle that looks kinda like a 'p' but not quite". It's insane.

Once there was a lecture at Yale, and Serge Lang, a frequent loud critic of bad notation was in the audience. There was a function Xi, and soon it was joined by its complex conjugation. Then they were divided. Serge Lang walked out.

That's delightful, but I fear many in the audience here may not quite see why. So, at the risk of explaining too much:

The Greek letter xi is one of those where the capital and lowercase versions are very different. Lowercase is a bit like a curly E. Uppercase is (at least if you're writing it in a hurry) basically three horizontal lines on top of each other.

The operation called complex conjugation can be notated in two ways, but the more common one among mathematicians is to put a horizontal bar above the thing being conjugated.

So the conjugate of Xi is ... four parallel horizontal lines.

And now we divide Xi (three horizontal lines) by Xi-bar (four horizontal lines), getting: eight horizontal lines.

In fact, here is the dreaded letter: Ξ And its lowercase version: ξ

The letter in actual use seems more likely to be printed as a two-tiered Z.

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