It is shown that the first order spectra of tetrahedrally coordinated amorphous semiconductors (TCAS) have a significantly large contribution from the allowed modes of the crystalline case. When these modes are not allowed in the crystalline case, e.g., infrared (IR) spectrum of Ge or Si, the spectrum will be composed entirely of the phonon density of state due to the relaxation of the wave vector (k⇒) conservation rule. A method involving the local changes of inter‐atomic distances or density in the amorphous (&agr;) state is presented which predicts the predominant dynamical disorder broadening of the first order spectra of such amorphous semiconductors.