What does W/W mean on say a bottle of shampoo?

For instance my son has some medicated shampoo the bottle says


W/W shampoo. What does W/W mean?What does W/W mean on say a bottle of shampoo?
wierd white shampooWhat does W/W mean on say a bottle of shampoo?
weight/weight.





ie. 1% W/W = 10 mg ingredient / 100 mg shampoo.
kickass is correct except his math example is not. 10 mg ingredient to 100 mg shampoo is 10 percent w/w not 1%
weight/weight