ever 用于以why，when，who 等开头的疑问句中，表示强调：“究竟，到底”。ever 的位置一般都在特殊疑问词之后。

You use ever in questions beginning with words such as 'why', 'when', and 'who' when you want to emphasize your surprise or shock.

Who ever can it be?

那究竟会是谁呢?

What ever is she doing?

她究竟在做什么?

Why ever didn't you tell me?

你究竟为什么不告诉我？

When ever am I going to see you again?

我到底什么时候再见到你？

【说明】ever 的这种强调用法，现代英语一般都是用合成词：wh-word+ever，例如：whatever, whoever, whenever, however, 唯独why ever 还是分开的。