a

发音： [ə ɡlɑːs ɒv ˈwɔːtə(r)]

a glass of water意思是：一杯水;

例句：

I pressed the juice of half a lemon into a glass of water.

翻译为：我用手将半个柠檬的汁挤入一杯水中。

I gave him a glass of water and he drank it thirstily.

翻译为：我给了他一杯水，他如饥似渴地喝了下去。

例句中的a glass of water都表示一杯水。