The caffeine content of coffee varies greatly, depending on the beans, how they're roasted, and other factors, but the average for an 8-ounce cup is about 100 milligrams (mg).
No, 'cat' is a common noun, a word for any cat of any kind. A proper noun is the name of a person, a place, a thing, or a title; for example: Cat Deeley, host of TV series 'So You Think You Can Dance'.
English grammar. Definition: Common nouns name any person, place, thing, or idea. They are not capitalized unless they come at the beginning of a sentence. Proper nouns are the names of specific people, places, things, or ideas. Proper nouns should always be capitalized.