instantiate

Instantiate means to create a concrete example from something more abstract or generic. In computing, to instantiate is to produce a concrete object or value that follows a defined class, type, or data structure. An instantiated object has its own state and can perform the behavior prescribed by its class or type. In philosophy and linguistics, the term can describe giving concrete existence to an abstract predicate or concept, yielding a particular case of it.

Etymology is reference to the noun instance, from Latin instantia, through the evolving usage in English. In computing, the term emphasizes the transition from a general specification to a specific, usable entity. This contrasts with related steps such as allocation (setting aside memory) and initialization (setting initial values).

In programming, instantiation typically involves invoking a constructor or factory method to create an object. For example, in Java, a class instance is created with syntax such as MyClass obj = new MyClass(args); in Python, obj = MyClass(args); and in JavaScript, const obj = new ClassName(args). Instantiation allocates storage for the new object and then runs initialization code to set initial field values. Distinctions are sometimes made between instantiation (creating the object) and initialization (establishing its initial state).

In logic and type theory, instantiation can also mean substituting a variable with a concrete term or type, producing an instance of a formula or polymorphic construct. Overall, instantiate is a general term used across disciplines to denote turning an abstract specification into a concrete, usable instance.