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

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

In the early eighteenth century, Georgia and Virginia used fines to penalize people for not voting.

From Salon • Dec. 31, 2024

On that measure, Migration Observatory calculations based on data from the European statistics agency Eurostat for 2022 puts the UK eighteenth out of the 32 European countries included.

From BBC • Oct. 25, 2023

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