They traveled to Shanghai in third class.

他们乘三等舱去上海旅行。

《新英汉大辞典》

youdao

Later in the third class, Mr. Du came in and asked me to go to the front.

后来到了第三节课时，杜老师进来叫我到前面去。

youdao

But it turns out actually over a third of people who took this class last year took the class because they felt depressed.

但是结果是去年有超过三分之一的人,选这门课是因为他们感觉抑郁。

哈佛公开课 - 幸福课课程节选

Okay. Now that's a lot of people in the class, maybe a third, a quarter, or half, something like that, a lot of people in the class.

好,班里很多同学,也许是三分之一,四分之一,或一半,班里很多人这样认为

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

And then third year when I taught it which was the last time, I had 850 students in the class, making it at that point the largest course at Harvard.

到了第三年，也就是上一次开课，有850人参加，是当时哈佛人数最多的课程。

哈佛公开课 - 幸福课课程节选

Bob Barton, from Llanarmon-yn-Ial near Ruthin, said it meant a "third class service" for some.

BBC: Collections at some rural post boxes were cut back in April

The medic who gave his life tending to his teammates -- Hospitalman Third Class James Layton.

WHITEHOUSE: The White House

We were third class and quite a lot of the third class children were not saved.

BBC: The last Titanic survivor, rescued aged nine weeks