Dehydration is the excessive loss of fluids in the body. Low levels of calcium and potassium may also cause muscle cramps, since both minerals contribute to healthy muscle function. Low blood supply to your legs and feet can cause cramping in those areas when you exercise, walk, or participate in physical activities.
Physical properties of materials and systems can often be categorized as being either intensive or extensive quantities, according to how the property changes when the size (or extent) of the system changes. According to IUPAC, an intensive property is one whose magnitude is independent of the size of the system.
The assay usually aims to measure an intensive property of the analyte and express it in the relevant measurement unit (e.g. molarity, density, functional activity in enzyme international units, degree of some effect in comparison to a standard, etc.).