Linear degenerate and genenuiely nonlinear???
In any elementary books about the conservation laws, we will come across the definitions of linear degenerate and genenuiely nonlinear waves. However, I never find the meaning of these two concepts, except the mathematic expressions about the eigenvalues and eigenvectors. Does any one know the meaning of these two guyes?

Re: Linear degenerate and genenuiely nonlinear???
For further study on this topic, I highly recommend Ami Harten's original paper on TVNI (Total Variation NonIncreasing), which was later abbreviated to TVD (Total Variation Diminishing).
"High Resolution Schemes for Hyperbolic Conservation Laws" (Ami Harten) Journal of Computational Physics, Volume 49, p.357393, 1983 On p.374 it talks about the two waves: "We consider here systems of conservation laws where the characteristic fields are either genuinely nonlinear (R a <> 0) or linearly degenerate (R a = 0). The waves of a genuinely nonlinear field are either shocks or rarefaction waves, depending whether the waves are convergent or divergent. The waves of a linearly degenerate field are exclusively contact discontinuities." In the above, 'R' is the matrix of right eigenvectors and 'a' is the vector of eigenvalues. The above paper is written by a mathematician and in my opinion is pretty hard to follow. If you want to read this stuff in 'plain English', then download my dissertation, where I talk about these concepts in detail (TVD, Euler Equations, Eigensytem, etc.), www.cfd4pc.com/papers.htm Let me know if you have any more questions! Axel 
Dear Axel Rohde
I need your dissertation where you talk about these concept in detail (TVD, Euler Equations, Eigen sytem, etc.) Your given link is not working. Thanks 
Dear Paul,
You may find some explanation in the book titled " I do like CFD,Vol 1", pages 4243. Below, I share the link of the same: https://books.google.co.in/books?id=...%20cfd&f=false 
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