* Common nouns refer to general, non-specific people, places, or things. They are not capitalized unless they start a sentence.
* Proper nouns refer to specific people, places, or things. They are always capitalized.
Examples:
* Common noun: The neighbors were friendly.
* Proper noun: I went to New York City last week.
Since "neighbors" refers to a general group of people who live nearby, it's a common noun.