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

eighteenths plural

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 )

Other Word Forms

Noun Inflected Forms

• eighteenths
  plural

Etymology

Origin of eighteenth

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

Example Sentences

See Examples For:

eighteenth eighteenths

The Dow Jones Industrial Average reached 48,500 points, marking its eighteenth record high of the year, reflecting market optimism.

From Barron's ● Dec. 11, 2025

It’s the negative image of an important intellectual movement of the seventeenth and eighteenth centuries, the Enlightenment, whose principles formed, among other things, the basis for American democracy.

From Salon ● Jun. 25, 2025

The Garrick was founded in 1831, named after famous eighteenth century actor David Garrick.

From BBC ● Mar. 20, 2024

The scrolls were discovered in the eighteenth century, when workmen came across the remains of a luxury villa that might have belonged to the family of Julius Caesar’s father-in-law.

From Scientific American ● Oct. 17, 2023

The ‘beyond reasonable doubt’ rule was formulated only in the eighteenth century, and the whole point of this rule is that juries have to decide for themselves what it means.

From "The Invention of Science" by David Wootton

As William II himself puts it, this day, like all the "eighteenths" that went before it, has its special significance.

From The Schemes of the Kaiser by Adam, Juliette

The faces of the volutes must recede from the edge of the abacus inwards by one and a half eighteenths of that same amount.

From The Ten Books on Architecture by Vitruvius Pollio

"There aren't two eighteenths of October in one year."

From A Sheaf of Corn by Mann, Mary E.