Notation and Symbols

1 Why This Page Exists

Many people are blocked less by ideas than by notation density. This page gives a small common language the rest of the site can rely on.

2 Frequent Symbols

  • \(\forall\) means “for all”
  • \(\exists\) means “there exists”
  • \(\in\) means “is an element of”
  • \(\subseteq\) means “is a subset of”
  • \(\mathbb{R}^n\) means \(n\)-dimensional real space
  • \(\|x\|\) means a norm or size of \(x\)
  • \(\langle x, y \rangle\) means inner product
  • \(\mathbb{E}[X]\) means expectation
  • \(\mathrm{Var}(X)\) means variance
  • \(A^\top\) means transpose

3 Reading Advice

When a formula feels dense:

  1. identify the objects
  2. identify the assumptions
  3. identify what is fixed and what is varying
  4. rewrite it in words once

That one habit makes a huge difference later.

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