The term "nineteenth" refers to the ordinal number that comes after eighteenth and before twentieth. It is commonly used to indicate the position of an item in a sequence, such as the nineteenth day of the month or the nineteenth century, which spans from 1801 to 1900. In mathematics, the fraction one-nineteenth (1/19) represents one part of a whole that is divided into nineteen equal parts. The concept of "nineteenth" can also apply to various fields, including music, where a nineteenth note may refer to a specific pitch or interval in a scale.