A more thorough explanation:

Contractus bonae fidei, vel stricti juris is a Latin term used in Roman law. It refers to contracts of good faith or of strict law. This means that the parties involved in the contract are required to perform their duties in good faith. In other words, they must act honestly and fairly towards each other. If a breach of contract occurs, a remedy can be sought.

For example, if two people enter into a contract for the sale of a car, they are expected to act in good faith. The seller must provide an accurate description of the car, and the buyer must pay the agreed-upon price. If either party fails to fulfill their obligations, the other party can seek a remedy.

All consensual contracts are considered contractus bonae fidei. This means that the parties must act in good faith, even if the contract does not explicitly state this requirement. Judges enforce contracts of good faith, such as contracts of sale, according to the requirements of good faith. Contracts of strict law, such as stipulations, are enforced according to their strict terms.

Sometimes, the term is shortened to contractus bonae fidei.