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Just as classes may be non-subclassable, method declarations may contain method modifiers that prevent the method from being overridden (i.e. replaced with a new function with the same name and type signature in a subclass). A private method is un-overridable simply because it is not accessible by classes other than the class it is a member function of (this is not true for C++, though). A final method in Java, a sealed method in C# or a frozen feature in Eiffel cannot be overridden.

If a superclass method is a virtual method, then invocations of the superclass method will be dynamically dispatched. Some languages require that method be specifically declared as virtual (e.g. C++), and in others, all methods are virtual (e.g. Java). An invocation of a non-virtual method will always be statically dispatched (i.e. the address of the function call is determined at compile-time). Static dispatch is faster than dynamic dispatch and allows optimizations such as inline expansion.

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