The point which shifts to the Decreasing drying period from the Constant drying period is called the Critical moisture content Wc.
The moisture content in which dryness does not advance any more is called the Equilibrium moisture content We.
In a general drying condition, the water (liquid) which can actually carry out evaporation removal is to the Equilibrium moisture content We.
The rate of the water (liquid) which can carry out evaporation removal to the Equilibrium moisture content We is called the Free moisture content Wf.
Wf = Free moisture content
Wi = Initial moisture content
We = Equilibrium moisture content
Wf = Wi - We
By the way, as shown in “1-1. What is drying.” in the strict sense, the moisture content W is different depending on the location in the interior of the wet material.
Expressed correctly, it become the following expressions of relations.
Related page:
1-6.The Local moisture content and the Average moisture content 
1-7.Drying characteristic curve – Relation between a drying rate and moisture content 
1-3.How to expressions the moisture in the material 
1-2.The phase shift of the ustulation 
3-5.Balance of the process 
1-8.Why is the constant drying period. – Moisture movement in wet material. 
1-1.What is drying 
1-4.Change of weight and the temperature by the drying