A more thorough explanation:

Definition: Reus stipulandi is a Latin term used in Roman law that refers to the party who asks questions in a stipulation. A stipulation is a formal contract where a promisor becomes bound by oral question and answer. The questioner in this contract is called the reus stipulandi or stipulator.

Examples: An example of a stipulation in modern times is when two parties agree to a certain condition or requirement in a contract. For instance, a contract may stipulate that a certain amount of money must be paid by a specific date. Another example is when attorneys representing opposing parties in a legal proceeding enter into a stipulation on a relevant point. For example, the plaintiff and defendant may stipulate on the issue of liability.

Explanation: The examples illustrate how a stipulation is a material condition or requirement in an agreement. It is a voluntary agreement between opposing parties concerning some relevant point. In the case of a legal proceeding, a stipulation made by a party to the proceeding or the party's attorney is binding without consideration. The reus stipulandi or stipulator is the party who asks the questions in a stipulation, and the promisor or reus promittendi is the party who answers the questions and becomes bound by the contract.