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'.
Definition. A proper noun is a noun belonging to the class of words used as names for unique individuals, events, or places. Contrast with common noun. Most proper nouns (for example, Fred, New York, Mars, Coca Cola) begin with a capital letter. Proper nouns are not usually preceded by articles or other determiners.