Definition:Metalanguage/Metasymbol

Definition
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, 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.

Also see
Altenative terms for a metasymbol are:
 * metalogical variable
 * metalogical symbol
 * metasyntactic variable.