The noun "quantity" can be both countable and uncountable.
Meaning: the amount of something
Example sentence: Economists mention both quality and quantity when they talk about the cost of production.
Meaning: a particular amount of something or number of things
Example sentence: The police raided several homes and found various quantities of illegal drugs.
Note: (for advanced students) When used as an uncountable noun, "quantity" usually refers to an abstract concept, esp. in economics or engineering, but when used as a countable noun, it usually refers to a particular amount of a concrete substance, or a particular number of concrete objects.
Test your understanding:
- In manufacturing, quantity greatly affects the cost of production.
- When larger quantities are manufactured, production cost per unit falls.