The Alphabet Everyone Assumes
Last timeFour Different Equals Signs
Greek letters, membership marks, bars and hats. None of them are explained anywhere, because everybody who writes them learned them from somebody who did not explain them either.
This lesson is a vocabulary list, which makes it the least interesting one in
the course and possibly the most useful. The marks in it are never explained,
because everybody who writes them learned them by absorption from somebody who
did not explain them either.
The Greek letters
There are twenty four Greek letters and about a dozen in regular use. What
matters is not pronouncing them but knowing the job each one usually has,
because that is a strong hint about what the formula is doing before you have
read any of it.
| Letter | Usually stands for |
|---|---|
| , alpha | a rate, especially a learning rate, or a mixing weight |
| , beta | a coefficient, or a momentum |
| , gamma | a discount on the future, or a scale |
| , delta | a small change, or a tolerance |
| , epsilon | a small quantity, usually in a claim about closeness |
| , theta | the parameters of a model, taken together |
| , lambda | the strength of a penalty, or a rate of arrival |
| , mu | a mean |
Two of these have the awkward property of meaning something different in
capitals. Capital sigma is the sum sign and lowercase sigma is a spread. Capital
pi is the product sign and lowercase pi is the constant. Both pairs are
unrelated, and both collisions are permanent.
The lesson stops here
7 more paragraphs to go
You have read the opening. The rest of the argument, the problems that check whether it landed, and the lines worth keeping at the end all come with a plan.
The first lesson of every course in the library reads the whole way through, free, so you can see exactly what the rest of them are.
See the planThe contentsThis is the reading half
Starting the course gives you your own copy of it. Every idea on every page has problems standing under it, marked with a reason rather than a tick, and any sentence you do not believe can be opened and argued with. None of that can happen on a page nobody owns.
The contents