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.

ˈthirtieth 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

After the thirtieth consecutive month without rain, the townsfolk of San Francisco de Conchos in the northern Mexican state of Chihuahua gather to plead for divine intervention.

From BBC • Jul. 13, 2025

All that we know is that he passed away in the intake room of the jail one day after his thirtieth birthday.

From Slate • Oct. 25, 2022

Earlier this month, Metallica released an expanded box set to commemorate the thirtieth anniversary of their fourth record, “. . . And Justice for All.”

From The New Yorker • Nov. 15, 2018

It took almost an hour before Alex learned that all the hospitals in Queens were scheduled for evacuation no later than Thursday, June thirtieth.

From "The Dead and the Gone" by Susan Beth Pfeffer