  We present a theoretical model for electromagnetically induced transparency
(EIT) in vapor, that incorporates atomic motion and velocity-changing
collisions into the dynamics of the density-matrix distribution. Within a
unified formalism we demonstrate various motional effects, known for EIT in
vapor: Doppler-broadening of the absorption spectrum; Dicke-narrowing and
time-of-flight broadening of the transmission window for a finite-sized probe;
Diffusion of atomic coherence during storage of light and diffusion of the
light-matter excitation during slow-light propagation; and Ramsey-narrowing of
the spectrum for a probe and pump beams of finite-size.
