Some of these signs can be considered "short-hands" in that they represent dipthongs.

有些可以表示双元音的符号看作是一种缩写。

youdao

Dipthongs are similar to ending consonants in that sometimes they are written and sometimes omitted.

双元音与词尾辅音类似，有时需要表示出来，有时则被省略。

youdao