Mi and Nautical mile

Mi noun - A former British unit of length equivalent to 6,080 feet (1,853.184 meters); 800 feet longer than a statute mile.

Nautical mile is a synonym for mi. In some cases you can use "Nautical mile" instead a noun "Mi".

Nautical mile noun - A unit of length used in navigation; exactly 1,852 meters; historically based on the distance spanned by one minute of arc in latitude.

Mi is a synonym for nautical mile. You can use "Mi" instead a noun phrase "Nautical mile".