markup – a percent added to the cost of an item to determine the selling price.
simple interest – a percent of an amount borrowed that is paid to the lender in addition to the amount borrowed.
tax – a percent of a purchase that is added to the purchase and paid to a government.
gratuity – a percent added on to the cost of a service.
commission – a percent of a sales amount awarded to the person making the sale. (taken out of the sale price and given to the sales person.)
discount – an amount subtracted from a regular price.