DEFINED as the ratio of mass of dry STEAM and combined mass of dry steam & mass of water in mixture. It is denoted by x.\(Dryness\;fraction\;\left( x \right) = \FRAC{{mass\;of\;vapour\;\left( {{m_v}} \right)}}{{mass\;of\;vapour\;\left( {{m_v}} \right) + mass\;of\;LIQUID\;\left( {{m_l}} \right)}}\)For saturated liquid x = 0For saturated vapour = 1The value of dryness fraction lies between 0 and 1.