cup 指有柄，用来饮茶或咖啡等的瓷杯。
glass 指玻璃制的杯子，用来盛酒和牛奶等东西。
mug 通常指周边垂直，不用茶托的有柄大瓷杯或大金属杯。
参考例句
1. Mother poured some milk into my glass. 母亲给我杯子里倒了些牛奶。
2. The best contraceptive is a glass of cold water: not before or after but instead. 最好的避孕方法是一杯冷水：不是在之前或之后，而是用它代替。
3. Know about the carpet shampoo, marble crystallization, glass cleaning, metal polishing and machine operation. 掌握地毯清洗、大理石结晶、玻璃刮洗、金属抛光和机器操作。
英英解释
n.
1. a brittle transparent solid with irregular atomic structure
2. a container for holding liquids while drinking
3. the quantity a glass will hold
4. a small refracting telescope
5. an amphetamine derivative (trade name Methedrine) used in the form of a crystalline hydrochloride; u
6. a mirror; usually a ladies' dressing mirror
7. glassware collectively v.
1. furnish with glass
2. scan (game in the forest) with binoculars
3. enclose with glass
4. put in a glass container
5. become glassy or take on a glass-like appearance
