Given the physical parameters of the ocean bottom, a plane wave reflection coefficientRpwcan be defined, e.g., the Rayleigh reflection coefficient.Rpw, or the equivalent bottom loss, is normally used in ray‐theory calculations. A reflection coefficient,per se, is not an explicit parameter in a normal mode formulation. [See H. P. Bucker, J. Acoust. Soc. Am.48, 1187–1194 (1971), for an exception to this.] For an inhomogeneous water column an effective plane wave reflection coefficientRecan be defined which plays the role of reflection coefficient in mode theory.ReandRpware equivalent only for an isovelocity water column. The phase ofReplays a direct role in determining the eigenvalues and contributes indirectly to the mode cycle or skip distancerC. The relationship betweenrCand the cycle distance arising from beam displacementrBD[E. L. Murphy, J. Acoust. Soc. Am.61, 511 (1977)] is shown to be an approximate one. It is further shown thatrBDis a fundamental constituent of mode theory and enters explicitly as a parameter in the mode amplitude. Several simple examples are selected to illustrate the various points. [Work supported by CNR/NORDA.]