What is the term for a means of specifying the syntax for valid commands in a programming language?

The correct answer is metalanguage, which refers to a type of language used to describe or analyze another language. In the context of programming languages, a metalanguage is employed to define the syntax and rules that govern how valid commands and expressions are structured. It provides a framework for understanding how elements of the programming language interact and are constructed.

While ‘grammar’ might seem like a fitting choice, as it also relates to the rules and structure of a language, metalanguage specifically emphasizes the descriptive aspect of those rules. In software development, a critical part of designing programming languages involves using metalanguages such as Backus-Naur Form (BNF) to articulate the formal syntax of commands.

The terms ‘syntax’ and ‘markup’ are more general and do not accurately encapsulate the concept of a language used to define another language's structure. Syntax refers to the arrangement of words and phrases to create well-formed sentences in a language, but it does not imply a descriptive framework itself. Markup typically refers to a system for annotating a document in a way that is syntactically distinguishable from the text, as seen in HTML or XML. Thus, the specific term that indicates the use of a language to describe the syntax of another language is