  This review represents a detailed and comprehensive discussion of the Thermal
Field Theory (TFT) concepts and key results in Yukawa-type theories. We start
with a general pedagogical introduction into the TFT in the imaginary- and
real-time formulation. As phenomenologically relevant implications, we present
a compendium of thermal decay rates for several typical reactions calculated
within the framework of the real-time formalism and compared to the
imaginary-time results found in the literature. Processes considered here are
those of a neutral (pseudo)scalar decaying into two distinct (pseudo)scalars or
into a fermion-antifermion pair. These processes are extended from earlier
works to include chemical potentials and distinct species in the final state.
In addition, a (pseudo)scalar emission off a fermion line is also discussed.
These results demonstrate the importance of thermal effects in particle decay
observables relevant in many phenomenological applications in systems at high
temperatures and densities.
