These definitions can be extended to the case of directed graphs.

This definition can be extended to the case when f takes values in some metric space.

The definition of absolute value given for real numbers above can be extended to any ordered ring.

The definition is also sometimes extended to included sounds made by humans in a directly biological way.

The definition has also been extended to include the common structure, principles and practices necessary to drive the organization.

The definition is sometimes extended to include those support staff without whom the above roles may struggle to function.

The definition can easily be extended to include any number of reagents.

The definitions can be extended to cover curves in higher dimensions.

This definition could be extended to cover activities such as:

This definition can be extended to rational functions as well.