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*natural*system of units is one in which the numerical values of ##c## and ##\hbar## are unity. However, they still have dimensions, indeed ##[c]=LT^{-1}## and ##[\hbar]=ML^{2}T^{-1}##. How is it the case then, that certain quantities, such as the action ##S##, can be treated as

*dimensionless*in natural units? Action has the same dimensions as ##\hbar##, so how can it be dimensionless? Is it simply that we consider the quantity ##S/\hbar##, which is already dimensionless, and then in natural units we have that ##S/\hbar =S## and we refer to this as the action?