thirtieth

American  

[thur-tee-ith] / ˈθɜr ti ɪθ /

adjective

1. next after the twenty-ninth; being the ordinal number for 30.

2. being one of 30 equal parts.

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noun

1. a thirtieth part, especially of one (1/30).

2. the thirtieth member of a series.

thirtieth British  

/ ˈθɜːtɪɪθ /

adjective

1. (usually prenominal)

   1. being the ordinal number of thirty in counting order, position, time, etc: often written 30th

   2. ( as noun )

      the thirtieth of the month

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noun

1. 1. one of 30 approximately equal parts of something

   2. ( as modifier )

      a thirtieth part

2. the fraction equal to one divided by 30 ( 1/ 30 )

Etymology

Origin of thirtieth

before 900; thirty + -eth ²; replacing Middle English thrittythe, Old English thrītegtha

Example Sentences

The difference: Your guests won’t have to feign enthusiasm after the thirtieth photo of you “holding up” the Leaning Tower of Pisa.

From The Wall Street Journal • Dec. 4, 2025

Hermen Hulst and his co-CEO Hideaki Nishino spoke to the BBC as Sony celebrates the thirtieth anniversary of the console being launched.

From BBC • Dec. 3, 2024

Find the thirtieth term of a sequence where the first term is −14 and the common difference is five.

From Textbooks • May 6, 2020

It’s hard to overlook, for instance, that this movie arrives in theatres in the same year as the thirtieth anniversary of Spike Lee’s “Do The Right Thing.”

From The New Yorker • Nov. 27, 2019

Among the sixteen official communiques sent on the thirtieth of April, 1944, is a missive to Berlin.

From "All the Light We Cannot See" by Anthony Doerr