predeclared

Predeclared refers to identifiers, such as variables, functions, types, or constants, that are available to code without explicit declaration by the user. These identifiers are provided by the language specification, the runtime environment, or the host application, and are considered part of the predeclared environment.

Predeclared symbols typically include built-in functions and types (for example, len or print in Python; Math or Date in JavaScript), keywords and primitive types, and global objects or namespaces supplied by the standard library. In addition to general programming languages, templating engines and domain-specific languages often define a set of predeclared identifiers that template authors can reference without declaring them.

The exact set of predeclared identifiers varies between languages and versions. Some systems permit shadowing, where a user-defined symbol can override a predeclared one in a local scope, while others prohibit redefinition to preserve safety and compatibility. The use of predeclared identifiers helps reduce boilerplate and makes common functionality readily accessible, but it can also lead to name collisions or unexpected behavior if the predeclared environment is not well documented.

In practice, understanding the predeclared environment is essential when debugging, refactoring, or porting code between environments, as assumptions about what is already available may differ. See also built-in functions, standard library, and template languages.