Analytical analysis of the nonlinear saturation of the Rayleigh-Taylor
(R-T) instability has been carried out and an appropriate physical mo
del has been proposed for the saturation mechanism. Stationary wave fo
rmalism and initial value approach have been applied for the analysis.
In the former case, a linear superposition model has been forwarded t
o understand the nonlinear saturation process, whereas in the latter,
the mode-mode coupling model. Parallel friction due to shear effect an
d ion polarization drift are identified as the basic sources of the no
nlinearity. Utility of the results in laboratory plasmas are highlight
ed.