glasses
n. C / Un. two pieces of glass or plastic in a frame that you wear over your eyes to see better. They can also protect your eyes from the sun.
n. a pair of lenses set in a frame and worn on the face to correct vision or protect the eyes. Plural in form and takes a plural verb.
I need to wear my glasses to read the menu.
She forgot her glasses at home, so she had to sit in the front row to see the screen.
Modern glasses often feature anti-reflective coatings and lightweight materials, making them far more comfortable for long-term wear than the heavy frames of previous decades.
When referring to the eyewear, it is a plural-only noun and takes a plural verb; use 'a pair of' to count them. In the sense of drinking containers, it is a standard countable noun.
I bought a new glassesI bought a new pair of glassesGlasses is a plural-only noun for eyewear; you cannot use the singular article 'a' without the phrase 'pair of'.