The name of a drug other than its trademarked (proprietary) name. The nonproprietary name for a new drug is usually the same as that selected by the United States Adopted Name (USAN) Council. The official names for older drugs may differ from the nonproprietary names. In some cases the generic name is the same as the nonproprietary name. Drugs also have chemical names; in most cases those names are too long and complex to permit their use. The use of a USAN selected name simplifies and standardizes drug nomenclature.