Here's why:

* Common nouns refer to general categories of people, places, or things.

* Proper nouns are specific names of people, places, or things.

"Science" is a broad term referring to the systematic study of the natural world. It's not a specific name of a person, place, or thing.

Examples:

* Common noun: The scientist conducted an experiment.

* Proper noun: Albert Einstein was a brilliant scientist.

Let me know if you have any other grammar questions! 😊