  Every physical system is characterized by its action. The standard measure of
integration is the square root of a minus the determinant of the metric. It is
chosen on the basis of a single requirement that it must be a density under
diffeomorphic transformations. Therefore, it may not be a unique choice. In
this thesis, we develop the two-measure and the Galileon measure string and
superstring actions, apply one of them to the string model of hadrons and
present the modified measure extension to higher dimensional extended objects.
