Comparative law notes
The function behind both the German and English concepts is to allow the supplier to reduce his or her price, at his or her discretion, and to reward certain customer conduct (loyalty, quick payments, "buy now" incentives). The German concept is a bit narrower and tied more closely to customer motivation to purchase. Be aware of a false friend, "rebate", which is understood among Americans as more of a partial refund, even though it often also results in what is effectively a discount.