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This video presents the basic differences of water activity and moisture content. Five differences are explained. First, water activity indicates the energy state of water in a food, i.e. higher energy state of water molecules create them mobile and reactive. Whereas moisture content indicates the amount of total water content in a food. A driving force, i.e. chemical potential is used to define the water activity, whereas there is no driving force used to define the water content. Standard is used to measure water activity, whereas standard is not required to measure moisture content. Water activity has no unit, i.e. it is a dimensionless number, whereas moisture content is presented with a unit in concentration either, wet basis or dry basis. I am going to explain both definitions later. Finally, water activity originates from equilibrium thermodynamics, whereas moisture content originates from composition. I have explained each point.