Drunk driving is the act of operating a motor vehicle with the operator's ability to do so impaired as a result of alcohol consumption, or with a blood alcohol level in excess of the legal limit. For drivers 21 years or older, driving with a blood alcohol concentration (BAC) of 0.08% or higher is illegal. For drivers under 21 years old, the legal limit is lower, with state limits ranging from 0.00 to 0.02. Lower BAC limits apply when operating boats, airplanes, or commercial vehicles. Among other names, the criminal offense of drunk driving may be called driving under the influence (DUI), driving while intoxicated or impaired (DWI), operating [a] vehicle under the influence of alcohol (OVI), or operating while impaired (OWI).