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'.
1 How Common Nouns Can Become Proper Nouns.  2 A proper noun and a common noun often combine to form the complete name of somethingâ Allegheny River, Bellevue Hospital âand in such formations, both the proper noun and the common noun are capitalized.ontrast with proper noun. As a general rule, a common noun does not begin with a capital letter unless it appears at the start of a sentence. Common nouns can be subdivided into count nouns and mass nouns. Semantically, common nouns can be classified as abstract nouns and concrete nouns.