9th

9th is the ordinal form of the number nine in English. It is used to indicate position or rank in a sequence, such as the ninth item in a list, the ninth day of a month, or the ninth edition of a publication. When written after a numeral, it appears as 9th; when spelling out the number, the word is ninth.

In English orthography, most ordinal numbers are formed with the suffix -th (for example, 4th, 5th, 6th, 7th, 8th, 9th, 10th). The exceptions are 1st, 2nd, and 3rd, which use the irregular endings. Thus 9th follows the standard -th pattern rather than a unique form.

Mathematically, 9 is the ninth positive integer. It is a composite number and a perfect square (3^2). Its divisors are 1, 3, and 9. In Roman numerals, the numeral for nine is IX.

The term 9th has broad usage beyond mathematics. It appears in dates (the 9th of May), geography and administration (for example, a city district such as the 9th arrondissement in Paris), and in contexts like rankings or editions (the 9th seed, the 9th edition of a work). It is also seen in legal or governmental designations, such as the Ninth Amendment to the United States Constitution.

Etymologically, 9th derives from the cardinal nine and the standard English ordinal suffix -th, applied to indicate order in a sequence.