A physical path taken by a signal or signal component that is either parallel to or relatively modestly transverse to the waveguide. Some signal components travel directly through the center of the waveguide, at least theoretically, and, therefore, travel the shortest possible distance between the point at which they enter the waveguide and the point at which they exit the waveguide. Other modes take more transverse paths, striking and reflecting off of the interface between the core and cladding as they propagate through an optical fiber, for example. Low-order modes take parallel or modestly transverse paths, while high-order modes take considerably more transverse paths. See mode for more detail. See also cladding, core, critical angle, high-order mode, and waveguide.