identifiers

An identifier is a name used to identify a variable, function, type, label, or other entity in a programming language or information system. Identifiers are defined by the lexical rules of the language or system and are distinguished from literals, operators, and keywords. They enable references to bindings at compile time or run time.

Naming rules vary by language and system. Common patterns include starting with a letter or underscore and continuing with letters, digits, or underscores. Some environments allow Unicode letters, while others restrict to ASCII. Identifiers are often case sensitive, meaning Foo and foo denote different identifiers, though some languages treat them as equivalent. Keywords or reserved words cannot be used as identifiers.

Identifiers exist within scopes or namespaces. A symbol table records the binding of an identifier to a memory location, type, or value. Shadowing can occur when an inner scope defines an identifier with the same name as one in an outer scope. Qualified names or namespace prefixes disambiguate identifiers across modules, packages, or databases.

In databases, identifiers name tables, columns, indexes, and other objects. They may require quoting to preserve case or include special characters, and some systems impose length limits or restrict certain words. In software development, best practices include choosing meaningful, consistent names, avoiding reserved words, and balancing brevity with clarity. Global identifiers such as UUIDs provide stable, system-wide uniqueness independent of naming.

Identifiers can also interact with localization and Unicode considerations. Some environments normalize identifiers to handle Unicode equivalence, reducing cross-platform confusion. Poorly chosen or conflicting identifiers can lead to bugs and maintenance challenges.