  The specificities of transverse polarization with respect to helicity of
ultrarelativistic fermions are pointed out. For massless fermions, a covariant
transversity four-vector is defined, up to a kind of gauge transformation. The
tranversity distribution of quarks in a nucleon is defined. Its possible
connection to the magnetic or electric dipole moment of the baryon is
conjectured. Consequences of the approximate chiral invariance on transverse
spin asymmetries in hard processes are enumerated. The "sheared jet effect"
introduced by Collins for measuring the transverse polarization of a final
quark is presented.
