The major performance measures for inhalation and nasal aerosols, sprays, and powders relate to dose delivery to the patient, including Delivered Dose Uniformity (DDU) and relevant measures of particle size (optical and/or aerodynamic) depending on the dosage form. Each of these is described in the following sections. A nomenclature table appears in Inhalation and Nasal Drug Products—General Information and Product Quality Tests 〈5〉 from which the descriptive terms for various dosage forms can be obtained.