Toward neutrino texture dominated by Majorana lefthanded mass matrix

A form of mixing matrix for three active and three sterile, conventional Ma jorana neutrinos is proposed. Its Majorana lefthanded part arises from the popular bimaximal mixing matrix for three active neutrinos that works satis factorily in solar and atmospheric experiments if the LSND effect is ignore d. One of three sterile neutrinos, effective in the Majorana righthanded an d Dirac parts of the proposed mixing matrix, is responsible perturbatively for the possible LSND effect by inducing one of three extra neutrino mass s tates to exist actively. The corresponding form of neutrino mass matrix is derived. If all three extra neutrino mass states get vanishing masses, the neutrino mass matrix is dominated by its specific Majorana lefthanded part. Then, the observed qualitative difference between mixings of neutrinos and down quarks may be connected with this Majorana lefthanded dominance reali zed for neutrinos. If m(1)(2) similar or equal to m(2)(2) for two of three basic neutrino mass states, the sum rule sin(2) 2 theta (sol) + sin(2) 2 th eta (Chooa)/2 + sin(LSND)(2 2 theta theta) = 1 holds in the two-flavor appr oximation (for each of three cases). Thus, the solar neutrino oscillation a mplitude, not fully maximal, leaves some room for the LSND effect, dependin g on the magnitude of Chooz effect (not observed so far).