The compound noun 'air force' is only a proper noun when it is used for a specific air force. For example:
Do we have an air force? Yes we do, the US Air Force. How do I join the Air Force? You visit an Air Force recruiter. Do other countries have an air force? Yes, most countries today do have an air force.
Note: The use of the capitalized noun Air Force is referring to a specific air force, the US Air Force, a proper noun even if the US is not mentioned, it is inferred. The lower case use of air force is not referring to a specific air force.
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Revolution is a common noun. If a common noun is part of a name, it becomes a proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
Robin is a proper noun when it is a name, but common when it is the bird. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. If a common noun is part of a name, it becomes a proper noun. Pronouns always replace proper and common nouns.
Olympic is a Proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are words for general things. Pronouns replace proper and common nouns.
Development is a common noun. Proper nouns are the unique names of people, places, or things. Common nouns are words for general things. Pronouns replace proper and common nouns.
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns always replace proper and common nouns.
Common nouns: capital, state, Austin Proper nouns: Texas
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Revolution is a common noun. If a common noun is part of a name, it becomes a proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
common
The common noun is person; the proper nouns are Spaniard and Spain.
Proper noun
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things.
Proper Nouns: Used to define the specific name of a noun. Common Nouns: The general form of nouns.
Two kinds of nouns are common or proper, singular or plural.
Proper nouns: New York City, Coca-Cola Common nouns: dog, table