In grammar, a proper noun refers to a type of word that names a unique and specific entity this includes the names of peoples, the names of places such as countries or cities, specific places such as museums, parks, rivers, and mountains, among others. Additionally, according to grammar, these types of words should be always capitalized in texts. Considering this, in the case of the sentence "After going to the store, brian put all the groceries away" the proper noun that has not been capitalized in the sentence is "Brian".
