Retention of title (a.k.a. reservation of title)
A retention of title clause is a contractual provision relating to the sale of goods that provides that the title/legal ownership of the goods is retained by the seller until full payment has been made for the goods.
In a sale of goods, if delivery is unconditional, physical possession of goods and the title to them passes together, as occurs in most standard retail purchases. However, a seller may also hand over goods conditionally, retaining title until the buyer has paid. A retention of title clause in a contract is often called a romalpa clause.