This lecture covers the concepts of fluid oscillators and amplifiers, focusing on the nonlinear saturation in oscillator flows and the nonlinear dynamics in amplifier flows. It discusses the linear and nonlinear analyses, frequency corrections, mean flow distortions, Reynolds stresses, bifurcation theory, and the Stuart-Landau amplitude equation. The instructor presents the normal form, resonance at third order, and the self-consistent model for turbulent mean and coherent flow. The lecture concludes with discussions on the quantitative agreement, mean flow decomposition, and the outline of the topics covered.