\begin{definition}[Definition:Metalanguage/Metasymbol]
A '''metasymbol''' is a symbol used in a metalanguage to represent an arbitrary collation in the object language.
'''Metasymbols''' are deliberately taken from a set of symbols that are '''not''' in the alphabet of the object language in question.
On {{ProofWiki}}, '''metasymbols''' are usually taken from any of:
: uppercase letters: $P, Q, R, \ldots$ and subscripted versions: $P_1, P_2, \ldots$
: the Greek alphabet: $\phi, \chi, \psi, \ldots$ and their subscripted versions: $\phi_1, \phi_2, \ldots$
: uppercase bold: $\mathbf A, \mathbf B, \mathbf C, \ldots$ and their subscripted versions: $\mathbf A_1, \mathbf A_2, \ldots$
Which system is in use on a particular page depends to a certain extent on the nature of the source work which has inspired it.
\end{definition}