Used to pull one person or thing OUT of a statement you have just made about a group — and here is the strange part: it goes AFTER the thing it removes. "Everyone was invited, John excepted" means everyone except John. "Sundays excepted, the shop opens at nine" means on all days but Sunday. This trailing position is what makes it feel old-fashioned and legal; you meet it on signs, in contracts, in notices ("present company excepted" is the set phrase people still say when they criticise a group and want to reassure the person in front of them). In everyday English almost nobody builds sentences this way — you would say except John, or apart from Sundays. Learn it mainly so you can read it. It is also simply the past form of the rare verb except, meaning to leave something out: "Children under six are excepted from the fee."