X-ray is already a proper noun.
proper
Is the x Ray is a proper noun
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Exxon is a proper noun
X-ray is already a proper noun.
proper
The word 'World X' is a proper noun, the name of a company, World X Productions, LLC. A proper noun is the name of a person, place, thing, or a title. A proper noun is always capitalized. However, the word is a common noun when not referring to the above company. For example, 'When world X conflicts with world Y, a science fiction tale is born.' This use of 'world x' is a common noun.
X-ray
Xavier
Is the x Ray is a proper noun
xanadu
The word x-ray is a common compound noun. The word Xbox is a proper compound noun.
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Pencil proper or common noun
proper noun
Exxon is a proper noun