The forms required by good breeding, or prescribed by authority, to be observed in social or official life; observance of the proprieties of rank and occasion; conventional decorum; ceremonial code of polite society.
Etiquette is all human social behavior. If you're a hermit on a mountain, you don't have to worry about etiquette; if somebody comes up the mountain, then you've got a problem. It matters because we want to live in reasonably harmonious communities. Judith Martin
You know, you can make a small mistake in language or etiquette in Britain, or you could when I was younger, and really be made to feel it, and it's the flick of a lash, but it would sting, and especially at school where there's not much privacy, and so on. You could, yes, undoubtedly be made to feel crushed. Christopher Hitchens