Dryness Fraction
Steam containing 5% moisture by mass, also contains 95% steam; the steam is described as having a dryness fraction of 0.95. Likewise, steam containing 1% moisture has a dryness fraction of 0.99. The equation to calculate a steam’s dryness fraction is:
A steam’s dryness fraction is an important consideration when determining how much heat is held by the steam. For example, wet steam always contains less energy than drier steam, thus drier steam makes the system process more efficient and is consequently desired.
The inverse of the dryness fraction is the wetness fraction, although this is less commonly quoted in steam tables than the dryness fraction.
Additional Resources
https://www.tlv.com/global/UK/steam-theory/wet-steam-dry-steam.html
https://www.electrical4u.com/steam-dryness-fraction
https://www.ques10.com/p/16727/define-i-dryness-fraction-ii-sensible-heat-of-wate