The reason the lisp is often written with a th-sound is that it's pretty impossible to write a fronted [s] with a normal keyboard.

口齿不清经常被误写为th音的原因是因为用一个普通键盘打出前移s音太困难了。

youdao

I'm always confused with "s" and "th".

我常把s和th搞混。

youdao

If s designates the sum of ages of employees 30 years and older across all slices and if s I is the sum within the i-th slice, it is easy to see that s is the sum of si.

如果s指定所有片上的年龄在30岁以上员工的年龄总和并且如果s i是第i片内的总和，那么很简单，S就是Si的总和。

youdao

Here's the problem. How do I get to the nth- er, the k'th element in the list, in this case?

如何找到第n个元素呢-,在这里，如何找到第k个元素呢？

麻省理工公开课 - 计算机科学及编程导论课程节选