multityped

Multityped is an adjective used to describe something that involves or can hold more than one data type. In computing, it often refers to values, expressions, or interfaces that are not restricted to a single type but may represent data of several types.

In programming language theory, multityped values are typically realized through sum types, union types, discriminated unions, or variant records. These constructs allow a single variable, field, or expression to take on values of different types, with runtime checks or compile-time guards to determine which type is in use. They enable flexible interfaces but can introduce complexity for type checking and error handling.

Examples include TypeScript's union types (for example, string | number) and language features such as Haskell's algebraic data types or Rust's enums, which encode multiple possible shapes or variants under one type. Using multityped values usually requires explicit type discrimination to ensure correct operations.

In data interchange and storage, multityped data may appear when a field can hold several kinds of values, such as JSON values that may be string, number, boolean, object, array, or null, or in databases that store variant data. Some schemas or languages provide dedicated mechanisms to model such variability, avoiding unsafe type casts.

See also: union type, discriminated union, variant, sum type, dynamic typing.