Proper nouns are specific names of people, places, or things.
For example:
* Person: John, Mary
* Place: London, Eiffel Tower
* Thing: iPhone, Mona Lisa
"Bus" is a common noun, referring to a general type of vehicle.
To make it a proper noun, you'd need to give it a specific name, like:
* The City Bus (referring to a specific bus company or route)
* The Red Bus (referring to a specific bus based on its color)
* The Big Blue Bus (referring to a specific bus based on its name)
Let me know if you have another word you'd like to find a proper noun for!