  Electroweak symmetry breaking and the origin of mass of fermion and boson are
fundamental questions to understand particle physics. The essential piece of
this symmetry breaking, the Higgs boson, is the most probable particle to be
discovered at the Large Hadron Collider (LHC). If one, or more, Higgs particles
are discovered, precise measurements of all the properties of this Higgs will
be very important including the measurement of Yukawa couplings of the fermions
to the Higgs. We present a study of e+e- -> ttH at a linear collider, with the
aim of making a direct measurement of the the top-Higgs coupling, g(ttH) using
the semi-leptonic final state and M_H of 120 GeV. We show that the top-Higgs
coupling at the center of mass energy 500 GeV, can be measured with an accuracy
of better than 28%.
