It is best to use a liquid measuring cup for liquids and a dry measuring cup for all solid foods. There is a slight difference in the measurement. That being said, cooking is not all that precise. An extra teaspoon or two here or there will make little difference in most recipes. Baking on the other hand is much more precise. If you are a serious baker you should consider using a kitchen scale which is much more accurate. If not then you should use dry and liquid cups properly.