eighteenth

American  

[ey-teenth] / ˈeɪˈtinθ /

adjective

1. next after the seventeenth; being the ordinal number for 18.

2. being one of 18 equal parts.

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noun

1. an eighteenth part, especially of one (1/18).

2. the eighteenth member of a series.

eighteenth British  

/ ˈeɪˈtiːnθ /

adjective

1. (usually prenominal)

   1. coming after the seventeenth in numbering or counting order, position, time, etc; being the ordinal number of eighteen: often written 18th

   2. ( as noun )

      come on the eighteenth

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noun

1. 1. one of 18 approximately equal parts of something

   2. ( as modifier )

      an eighteenth part

2. the fraction that is equal to one divided by 18 ( 1/ 18 )

Etymology

Origin of eighteenth

before 900; Middle English eightenthe, eightethe, Old English eahtatēotha. See eighteen + -th ²

Example Sentences

Eighteenth century activities included croquet and designing a custom perfume, all accompanied by fashion photography.

From Los Angeles Times • May 4, 2026

The image was taken in the Eighteenth Century Room at Buckingham Palace three days after Elizabeth died.

From Seattle Times • Sep. 24, 2022

The image was taken in the Eighteenth Century Room at Buckingham Palace last week.

From Reuters • Sep. 23, 2022

She then used that material to revolutionize historians’ understanding of slavery in her book “Africans in Colonial Louisiana: The Development of Afro-Creole Culture in the Eighteenth Century,” published in 1992.

From New York Times • Sep. 11, 2022

Few laws or acts of Congress have ever been so unpopular with so many people as the Eighteenth Amendment.

From "1919 The Year That Changed America" by Martin W. Sandler