In the natural semantic metalanguage theory, explications are semantic representations of vocabulary. SCSS is a nested metalanguage, as valid CSS is valid SCSS with the same semantics. Naur form (BNF) is a formal metalanguage originally used to define ALGOL 60. The paradigmatic example of a nested metalanguage comes from the Linnean taxonomic system in biology. Metacompilers differ from parser generators, taking as input a program written in a metalanguage. COBOL's syntax is usually described with a unique metalanguage using braces, brackets, bars and underlining. An embedded metalanguage is a language formally, naturally and firmly fixed in an object language. OWL is a metalanguage, including a basic grammar, but without a dictionary. The language used to make statements about an object language is called a "metalanguage". Any language that one uses to talk about a formal system is called a "metalanguage". The development of a programming language involves the use of a metalanguage. An ordered metalanguage is analogous to an ordered logic. The language in which the metaprogram is written is called the metalanguage. In describing the transformation rules, we may introduce a metalanguage symbol formula 70. There are several entities commonly expressed in a metalanguage.