One essential feature of plasma media is supporting various plasma waves and dictating electromagnetic wave propagation. This textbook provides students with an understanding of plasma waves, which is key to theoretical and experimental plasma research and understanding the experimental results, and will enable them to expand their studies into related areas. The first part of the text provides the basis of plasma modes, including the formulations, analyses and the physical characterizations. The second part introduces techniques for the studies of wave propagation in inhomogeneous plasma and of nonlinear mode-mode coupling in turbulent plasma as well as in active plasma, applied to exemplify the excitation of parametric instabilities in high-frequency (HF) wave heated ionospheric plasma. The third part introduces nonlinear plasma waves of periodic function forms and of solitary forms; a potential application of the HF wave-ionosphere interaction for setting up an ionospheric very-low-frequency transmitter for underwater communications is introduced. This is also a useful reference book for researchers in the areas of plasma physics and engineering, and in geophysics.