Is cup a countable or uncountable noun?

"Cup" can be both a countable and an uncountable noun, depending on how it's used.

Countable:

* When referring to individual cups as objects: "I have three cups of coffee."

* When referring to a specific type of cup: "She bought a tea cup."

Uncountable:

* When referring to the liquid contained within a cup: "He drank a cup of tea." (Here, "cup" refers to the amount of liquid, not the container itself)

Therefore, it's important to pay attention to the context to determine whether "cup" is countable or uncountable.