A proper noun is a specific name used to identify a particular person, place, or organization. Unlike common nouns, which refer to general items (like "city" or "book"), proper nouns are always capitalized. Examples include New York, Eiffel Tower, and Albert Einstein. Proper nouns help distinguish unique entities from others in language. They provide clarity and specificity, allowing us to refer to distinct subjects. For instance, saying "I visited Paris" indicates a specific city, while "I visited a city" does not specify which one.