什麼情況下glass用單數
來源：魅力女性吧 2W
glass 表示玻璃，玻璃杯的時候是單數，但當glasses 意思眼睛的時候，當作複數。
例句
A glass of water is on the desk.
There is a glass of water on the desk.
The window glass is shining under the sun.
He always wears glasses.
When the sun shines brightly， people usually wear sun glasses.
