A more thorough explanation:

Definition: Stipulatio sponsalitia was a solemn promise made by a father in early Roman law that his child would marry someone else's child. In some cases, there was a penalty if the marriage did not occur. However, in classical and later Roman law, such a promise was considered immoral and unenforceable.

Example: A father promises another father that his son will marry the other father's daughter. If the marriage does not occur, the father who made the promise may have to pay a penalty.

This example illustrates the concept of stipulatio sponsalitia, where a father makes a promise regarding the marriage of his child. However, as mentioned in the definition, such promises were later considered immoral and unenforceable.

Definition: A stipulator is someone who makes a stipulation. In civil law, a stipulator can also be the promisee in a stipulation pour autrui, accepting the promise of a benefit to a third party.

Example: A person promises to give a gift to their friend's child if the child graduates from college. The friend accepts the promise on behalf of their child. In this case, the friend is the stipulator.

This example illustrates the concept of a stipulator in civil law, where the promisee accepts a promise made for the benefit of a third party.