stain

我意识到我的裤子上有一个污渍。

I realized that I had a ___stain on my trousers.

我意识到我裤子上有一个污渍。

I realised that I had a ___stain on my trousers.

枕头上的暗红色污渍让他感到不安。

A dark red ___stain on the pillow made him uneasy.