Proper nouns are the specific terms used to refer to individual people, places, and things. They are always capitalized and are used to differentiate between similar things. Some synonyms for proper nouns include personal nouns, specific nouns, unique nouns, formal nouns, and named nouns. Personal nouns are names given to individuals, while specific nouns are names given to particular things or places. Unique nouns refer to items that have no identical item, while formal nouns refer to words used in formal language. Named nouns are words that have been specifically given a name. All of these synonyms can be used interchangeably with proper nouns depending on the context.