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From Why start at x, y, z

This is a collection of ambiguous, inconsistent, or just unpleasant conventions in mathematical notation, started by Christian Lawson-Perfect.

For each bit of notation, I want to collect examples, alternatives, and references to discussions about them.

The site's name is a reference to the question about why we start naming variables at 𝑥.

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  • Ambiguities - notations which can be reasonably interpreted in more than one way
  • Conflicting definitions - definitions of terms or mathematical objects that don't have a single universally recognised meaning
  • Handwriting - things that only or mainly come up in handwritten notation.
  • Inconsistencies - conventions in notation that are inconsistent with each other, and conventions that could apply more generally, but for some reason don't.
  • Language - problems to do with mathematical language.
  • Local variations - conventions in notation that are particular to a place or group of people.
  • Unpleasantness - conventions that just make you feel yuck.

How to contribute

You can edit this site, once you've created an account.

My aim is to describe conventions, without prescribing a correct notation.

While the tone of the site is informal, please avoid writing in a way that would make someone who follows a certain convention feel bad.