The terms driving under the influence (DUI), driving while impaired (DWI), and operating a vehicle under the influence (OVI) are all legal phrases that refer to the crime of operating a vehicle while impaired by drugs (illegal or prescription), alcohol, or both. These terms are largely interchangeable though some states use only one acronym in their statutes for the sake of clarity. There are also other acronyms occasionally substituted for DUI, such as DWAI (driving while ability impaired), OWI (operating while intoxicated), OUI (operating under the influence), and DUII-CS (driving under the influence of intoxicants: controlled substances).