  Aims: Following our comprehensive studies of the WR stars in the Milky Way,
we now present spectroscopic analyses of almost all known WN stars in the LMC.
Methods: For the quantitative analysis of the wind-dominated emission-line
spectra, we employ the Potsdam Wolf-Rayet (PoWR) model atmosphere code. By
fitting synthetic spectra to the observed spectral energy distribution and the
available spectra (ultraviolet and optical), we obtain the physical properties
of 107 stars. Results: We present the fundamental stellar and wind parameters
for an almost complete sample of WN stars in the LMC. Among those stars that
are putatively single, two different groups can be clearly distinguished. While
12% of our sample are more luminous than 10^6 Lsun and contain a significant
amount of hydrogen, 88% of the WN stars, with little or no hydrogen, populate
the luminosity range between log (L/Lsun) = 5.3...5.8. Conclusions: While the
few extremely luminous stars (log (L/Lsun) > 6), if indeed single stars,
descended directly from the main sequence at very high initial masses, the bulk
of WN stars have gone through the red-supergiant phase. According to their
luminosities in the range of log (L/Lsun) = 5.3...5.8, these stars originate
from initial masses between 20 and 40 Msun. This mass range is similar to the
one found in the Galaxy, i.e. the expected metallicity dependence of the
evolution is not seen. Current stellar evolution tracks, even when accounting
for rotationally induced mixing, still partly fail to reproduce the observed
ranges of luminosities and initial masses. Moreover, stellar radii are
generally larger and effective temperatures correspondingly lower than
predicted from stellar evolution models, probably due to subphotospheric
inflation.
