I understand that the dynamic modulus of a material is measured by inducing a sinusoidal force and measuring the strain response. Usually one gets a value for the storage and loss modulus. However, I don't understand how one would "quantify" how viscous a material is. I know a viscous material (less elastic) has a higher loss modulus and a lower storage modulus. But is there a certain ratio of the two variables where one considers a material mostly elastic or mostly viscous? I guess it would be easier if I can get a value for the dynamic modulus for some common materials. In addition, I understand the dynamic modulus is dependent on the frequency. So which frequency is common one to use when judging how viscous / elastic a material is?