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---
# typename
In template definitions, provides a hint to the compiler that an unknown identifier is a type. In template parameter lists, is used to specify a type parameter.  
  
## Syntax  
  
```  
  
typename identifier;  
```  
  
## Remarks  
 This keyword must be used if a name in a template definition is a qualified name that is dependent on a template argument; it is optional if the qualified name is not dependent. For more information, see [Templates and Name Resolution](../cpp/templates-and-name-resolution.md).  
  
 **typename** can be used by any type anywhere in a template declaration or definition. It is not allowed in the base class list, unless as a template argument to a template base class.  
  
```  
template <class T>  
class C1 : typename T::InnerType // Error - typename not allowed.  
{};  
template <class T>  
class C2 : A<typename T::InnerType>  // typename OK.  
{};  
```  
  
 The **typename** keyword can also be used in place of **class** in template parameter lists. For example, the following statements are semantically equivalent:  
  
```  
template<class T1, class T2>...  
template<typename T1, typename T2>...  
```  
  
## Example  
  
```  
// typename.cpp  
template<class T> class X  
{  
   typename T::Y m_y;   // treat Y as a type  
};  
  
int main()  
{  
}  
```  
  
## See Also  
 [Templates](../cpp/templates-cpp.md)   
 [Keywords](../cpp/keywords-cpp.md)