WordReference Collins English Usage © 2020
A person's glasses are two pieces of glass in a frame which they wear to help them to see better.
He took off his glasses.
Who is that girl with red hair and glasses?
Glasses is a plural noun. Don't talk about ‘a glasses’. Instead say a pair of glasses.
Li has a new pair of glasses.
After glasses you use a plural form of a verb. After a pair of glasses you use a singular form.
Your glasses are on the table.
A pair of glasses costs a lot of money.
WordReference Collins English Usage © 2020
cup - glass - mug
A cup is a small, round container, usually with a handle, from which you drink hot drinks such as tea and coffee. When you are not holding a cup, you usually rest it on a saucer.
John put his cup and saucer on the coffee table.
A cup is also a unit of measurement used in cooking.
Mix four cups of flour with a pinch of salt.
A glass is a container made out of glass and used for cold drinks.
I put down my glass and stood up.
He poured Ellen a glass of juice.
A mug is a large deep cup with straight sides and a handle, used for hot drinks. You don't rest a mug on a saucer.
He spooned instant coffee into two of the mugs.
containers and contents
You can use cup, glass, and mug to talk about either the containers or their contents.
I dropped the cup and it broke.
Drink eight glasses of water a day.
'glasses' also found in these entries:

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