17th

17th is the ordinal form of the cardinal number 17, used to indicate position in a sequence. In English, ordinals are written with the suffix -th after the number’s spelling (seventeenth) or as 17th in numerals. The suffix -th is common, with 1st, 2nd, and 3rd used for numbers ending in 1, 2, or 3 in certain contexts.

In everyday use, 17th is applied to dates, chapters, rankings, and other ordered items. For example, the 17th day of a month is written as the 17th; the 17th chapter follows the 16th, and so on. It appears in formal titles and lists to denote sequence.

Notable uses in history and science include the 17th Amendment to the United States Constitution, ratified in 1913, which established the direct election of U.S. Senators. The 17th century spans roughly 1601 to 1700. The 17th parallel was the provisional military demarcation line for Vietnam following the Geneva Accords. Andrew Johnson served as the 17th president of the United States (1865–1869). In science, the element with atomic number 17 is chlorine (Cl), and the number 17 is a prime number (the 7th prime is 17; the 17th prime is 59).