Final answer:
The key difference between proper and common nouns lies in their specificity. Common nouns are general, while proper nouns are specific and always capitalized.
Step-by-step explanation:
The key difference between a proper and common noun lies in their specificity. Common nouns are general and refer to people, places, or things in a common or general sense. For example, 'book', 'city', or 'teacher' are common nouns. On the other hand, proper nouns refer to specific people, places, or things and are always capitalized. Examples of proper nouns include 'Harry Potter', 'New York City', or 'Ms. Johnson'.
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