Sign convention

Annoyingly often in physics, some textbooks and articles would use definitions for certain quantities 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.
• The sign of work in the first law of thermodynamics.

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.