Wet steam and specific volume.
The droplets of water in wet steam occupies negligible space in the steam and the specific volume of wet steam will be reduced according the dryness fraction:
v = vs ζ (1)
v = specific volume of wet steam (m3/kg, ft3/lb)
vs = specific volume of the dry steam (m3/kg, ft3/lb)
ζ = dryness fraction