  Sulphur is an element which is formed in the alpha-process and is easily
measured in the gaseous phase in external galaxies. Since it does not form
dust, it is the preferred indicator for alpha-elements, rather than Si or Mg,
for which dust corrections are necessary. The measurement of the sulphur
abundance in stars is not an easy task, relying mainly on high excitation lines
with non-negligible deviations from LTE. The 1082 nm sulphur forbidden
transition is less sensitive to departures from LTE and is less dependent on
temperature uncertainties than other sulphur lines usually employed as
abundance indicators. Therefore it should provide a more robust abundance
diagnostics. aims: To derive the solar photospheric abundance of sulphur from
the 1082 nm [SI] line and to investigate 3D effects present in G- and F-type
atmospheres at solar and lower metallicity. method: High-resolution, high
signal-to-noise solar intensity and flux spectra were used to measure the
sulphur abundance from the [SI] 1082 nm line. co5bold hydrodynamical model
atmospheres were applied to predict 3D abundance corrections for the [SI] line.
results: The solar sulphur abundance is derived to be 7.15+- (0.01)stat +-
(0.05)sys, where the statistical uncertainty represents the scatter in the
determination using four different solar spectra and the systematic uncertainty
is due to the modelling of the blending lines. Sulphur abundances obtained from
this line are insensitive to the micro-turbulence. 3D abundance corrections,
found from strictly differential comparisons between 1D and 3D models, are
negligible in the Sun, but become sizable for more metal-poor dwarfs.
