I think the main reason is that there are no equations that involve the third derivative explicitly.

我想主要原因是因为还没有等式,明显涉及三阶导数

耶鲁公开课 - 基础物理课程节选

Third floor is where I live. That's substance-free, no alcohol and no drinking.

我住在三层。那是无饮酒区，没有酒精，不许喝酒。

布朗的宿舍公寓 - SpeakingMax英语口语达人

The third plague in each set has no forewarning and no introduction.

每组的第三次瘟疫即没有预先示警，也没有任何指令。

耶鲁公开课 - 旧约导论课程节选

And then there is this third species, the neutron, which has no charge.

这是第三种了，中子，不带电。

麻省理工公开课 - 固态化学导论课程节选

Where even if you can find somebody who's going to be a first quartile manager, there's almost no difference between the first quartile return and the third quartile return.

即使你能找到一位,一流的经理人,但在债券市场收益中,第一和第三个四分位数之间几乎没有区别

耶鲁公开课 - 金融市场课程节选

No, George the Third was probably dead by then.

不对,乔治三世那时候可能已经死了

耶鲁公开课 - 聆听音乐课程节选