[1] Expressions in a metalanguage are often distinguished from those in the object language by the use of italics, quotation marks, or writing on a separate line.
[citation needed] The structure of sentences and phrases in a metalanguage can be described by a metasyntax.
This idea is found in Douglas Hofstadter's book, Gödel, Escher, Bach, in a discussion of the relationship between formal languages and number theory: "... it is in the nature of any formalization of number theory that its metalanguage is embedded within it.
"[3] It occurs in natural, or informal, languages, as well—such as in English, where words such as noun, verb, or even word describe features and concepts pertaining to the English language itself.
The paradigmatic example of a nested metalanguage comes from the Linnean taxonomic system in biology.
In a natural language there is an infinite regress of metalanguages, each with more specialized vocabulary and simpler syntax.
Metalanguages of formal systems all resolve ultimately to natural language, the 'common parlance' in which mathematicians and logicians converse to define their terms and operations and 'read out' their formulae.
, they are metavariables in the metalanguage (in this case, English) that is discussing the object language
A metatheorem is a true statement about a formal system expressed in a metalanguage.
The major framework views language as a sealed pipeline between people: The minor framework views language as an open pipe spilling mental content into the void: Computers follow programs, sets of instructions in a formal language.
Backus–Naur form, developed in the 1960s by John Backus and Peter Naur, is one of the earliest metalanguages used in computing.
Examples of modern-day programming languages which commonly find use in metaprogramming include ML, Lisp, m4, and Yacc.