  We present a unified description of the spontaneous symmetry breaking and its
associated bosons in fermion field theory. There is no Goldstone boson in the
fermion field theory models of Nambu-Jona-Lasinio, Thirring and QCD$_2$ after
the chiral symmetry is spontaneously broken in the new vacuum. The defect of
the Goldstone theorem is clarified, and the "massless boson" predicted by the
theorem is virtual and corresponds to just a $free$ massless fermion and
antifermion pair. Further, we discuss the exact spectrum of the Thirring model
by the Bethe ansatz solutions, and the analytical expressions of all the
physical observables enable us to understand the essence of the spontaneous
symmetry breaking in depth. Also, we examine the boson spectrum in QCD$_2$, and
show that bosons always have a finite mass for $SU(N_c)$ colors. The problem of
the light cone prescription in QCD$_2$ is discussed, and it is shown that the
trivial light cone vacuum is responsible for the wrong prediction of the boson
mass.
