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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.

Like all language, mathematical notation is just something we make up to help express our ideas, and opinions, abuses of notation, lapses in memory and convenience all work against consistency and clarity.

The site's name is a reference to the question about why we start naming variables at 𝑥. The logo is a drawing of the stacked fraction \(\frac{\bar{\Xi}}{\Xi} \).


  • 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.
  • Unspoken conventions - conventions that aren't typically formalised, but are widely followed.
  • Variable Names - conventions for assigning symbols or other identifiers to variables.
  • References - links to material that might help when filling in this site.
  • Needs filling in - pages that have maybe a link or two, but need filling in with text.

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.

We're still working out how the site should be organised. Please add your thoughts at Whystartatxyz:Organisation.