Producing a more defined version of some object by replacing variables with values (or other variables).

1. In object-oriented programming, producing a particular object from its class template. This involves allocation of a structure with the types specified by the template, and initialisation of instance variables with either default values or those provided by the class's constructor function.

2. In unification, (as used in logic programming, type checking and type inference), binding a logic variable (type variable) to some value (type).