A more thorough explanation:

Addictio in diem

Addictio in diem is a clause in a contract of sale that allows the contract to be terminated if the seller receives a better offer within a specified period. This means that if someone offers to buy something for more money than the original buyer, the seller can cancel the original sale and sell to the new buyer instead.

• John agrees to buy a car from Sarah for $10,000. They include an addictio in diem clause in the contract that allows Sarah to cancel the sale if she receives a better offer within the next 7 days. On the 5th day, someone offers Sarah $12,000 for the car. She cancels the sale with John and sells the car to the new buyer instead.
• Emily signs a contract to buy a house from Tom for $500,000. The contract includes an addictio in diem clause that allows Tom to cancel the sale if he receives a better offer within the next 30 days. No one makes a better offer, so the sale goes through as planned.

These examples show how addictio in diem works in a contract of sale. It gives the seller the option to cancel the sale if they receive a better offer, which can be beneficial for them if they want to make more money. However, it can also be risky for the buyer, who may lose out on the item they wanted to purchase.