Introduction: The basic equations; Turbulence models; Filter operations -- Stochastic variables: PDFs of one variable; The characterization of PDFs by moments; PDFs of several variables; Statistically most-likely PDFs; Examples for statistically most-likely PDFs; Examples for other PDFs; Theta and delta functions -- Stochastic processes: PDF transport equations; The Fokker-Planck equation; An exact solution to the Fokker-Planck equation; Stochastic equations for realizations; Stochastic modeling; The dynamics of relevant variables -- The equations of fluid and thermodynamics: The fluid dynamic variables; From the molecular to fluid dynamics; The closure of the fluid dynamic equations; The equations for multicomponent reacting systems; Direct numerical simulation; Reynolds-averaged Navier-Stokes equations; Second- and higher-order RANS equations -- Stochastic models for large-scale turbulence: A hierarchy of stochastic velocity models; The generalized Langevin model for velocities; A hierarchy of Langevin models; The Kolmogorov constant; A hierarchy of stochastic models for scalars; Compressible reacting flow: velocity models; Compressible reacting flow: scalar models; Stochastic models and basic equations; Consistent turbulence models; Nonlinear stochastic models -- Stochastic models for small-scale turbulence: The generalization of LES by FDF methods; The closure of the equation for filtered velocities; The closure of the scalar FDF transport equation; The closure of LES and FDF equations; The dynamic eddy length scale calculation; The scalar-conditioned convective flux; An assumed-shape FDF method -- The unification of turbulence models: The need for the unification of turbulence models; Unified turbulence models; Some unsolved questions. References -- Author index -- Subject index.