Annoyingly often in physics, some textbooks and articles would use definitions for certain quatities with the opposite sign from other textbook/articles. This lack of standardization is a frequent source of confusion, misunderstandings and even outright errors. A choice of signs in the definition is called a sign convention. Sometimes, this term is used more sloppily to include factors of i and 2&pi.

A noncomprehensive list of sign conventions:

• In relativity, the metric signature could either be +--- or -+++.
• The choice of in the Dirac equation.
• The sign of the Faraday 2-form in gauge theories.

It is often considered good form to explicitly state which sign convention you are using at the beginning of every article/book.

Warning: Since this encyclopedia is written by hundreds of different mathematicians/physicists, there is absolutely no guarantee of consistency in sign conventions here. Proceed at your own peril.

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