Reabsorption of vapor refers to the dampness absorbed by clay from the air. The quantity depends on the dampness of the atmosphere, which can change from day to day and room to room. Clay can accept these adjustments, but when completely dry, if it reabsorbs moisture, this will cause a slight expansion. Some parts are finer than others and reabsorb dampness quicker than the thicker parts this makes a tension between different thicknesses and can cause cracking or breaking.
Re-absorption of water refers to water being added to dry clay, so as to make it more pliable