# Symbols:Abbreviations/Q

Jump to navigation
Jump to search

## Q

### Q.E.D.

The initials of **Quod Erat Demonstrandum**, which is Latin for **which was to be demonstrated**.

These initials were traditionally added to the end of a proof, after the last line which is supposed to contain the statement that was to be proved.

The usage is considered hopelessly old-fashioned nowadays, and is rarely seen outside nerd sitcoms.

The Halmos symbol $\blacksquare$ is usually used instead.

$\mathsf{Pr} \infty \mathsf{fWiki}$ universally uses $\blacksquare$ to signify the end of a proof.

The symbol $\Box$ is used to signify the end of a stage part way through a proof, where a subsidiary result is proved.