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.