Instantiation

Instantiation is the process of turning an abstract concept into a concrete example. It commonly refers to creating a specific instance from a general specification.

In programming, instantiation means creating an object from a class or a template. When a program runs, a constructor initializes the object's state, allocates memory, and binds methods to the object. The resulting object is an instance of the class. Multiple objects can be created from the same class. In Java, for example, an object is created with new ClassName(args).

In logic and mathematics, instantiation involves substituting a variable in a formula with a concrete term to obtain a specific instance. Universal instantiation applies a general statement to any chosen element, while existential instantiation asserts that some example exists. In model theory, a structure interprets a formula by substituting elements of the domain for its variables.

In type theory and programming languages with generics, instantiation (also called specialization) substitutes a type variable with a concrete type, producing a specialized version of a generic function or data type. This can enable type-specific optimizations and concrete usage of polymorphic code.

Beyond formal contexts, instantiation can also refer to the concrete realization of a general idea or property as a particular case or example. The term emphasizes the move from abstract description to a tangible, usable instance.