Partial template specialization is a particular form of class template specialization. Usually used in reference to the C++ programming language, it allows the programmer to specialize only some arguments of a class template, as opposed to explicit full specialization, where all the template arguments are provided. Templates and specialization Class templates are really meta-classes: they are partial abstract data types that provide instructions to the compiler on how to create classes with the proper data members. For example, the C++ standard containers are class templates. When a programmer uses a vector, one instantiates it with a specific data type, for example, int, string or double. Each type of vector results in a different class in the compiler's object code, each one working with a different data type. This process is called monomorphization of generics. If one knows that a class template will be used with a specific data type fairly often and this data type allows some optimizations (e.g. bit shifting with integers, as opposed to multiplying or dividing by 2), one may introduce a specialized class template with some of the template parameters preset. When the compiler sees such a class template instantiated in code, it will generally choose the most specialized template definition that matches the instantiation. Therefore, an explicit full specialization (one where all the template arguments are specified) will be preferred to a partial specialization if all the template arguments match. Partial specialization Templates can have more than one parameter type. Some older compilers allow one only to specialize either all or none of the template's parameters. Compilers that support partial specialization allow the programmer to specialize some parameters while leaving the others generic. Example Suppose there exists a KeyValuePair class with two template parameters, as follows. template <typename Key, typename Value> class KeyValuePair {}; The following is an example of a class that defines an explicit full template specialization of KeyValuePair by pairing integers with strings. The class type retains the same name as the original version. template <> class KeyValuePair<int, std::string> {}; The next is an example of partial specialization of KeyValuePair with the same name as the original version and one specialized template parameter. template <typename Key> class KeyValuePair<Key, std::string> {}; The next example class KeyStringPair is derived from the original KeyValuePair with a new name, and defines a partial template specialization. In contrast to the explicit specialization above, only the Value template