Except that's not a  Y, it's a thorn.

但那不是一个 Y，而是一根刺。

The basic structure is if x happens I will do y, a common example that most of us already follow is when I wake up I'll brush my teeth.

基本的结构是，如果 x 发生，我就会做 y，一个常见的例子，我们大多数人已经遵循了，当我醒来时，我就会刷牙。

It really came into its own during the Middle English period, so between the 1100s and the 1400s, where it could replace both a Y or a GH.

它在中古英语时期真正崭露头角，因此在 1100 年代和 1400 年代之间，它可以取代 Y 或 GH。