A more thorough explanation:

Contemporanea expositio is a Latin term that means "contemporaneous exposition." It refers to the doctrine that the best interpretation of a statute or document is the one given by those who enacted or signed it. This doctrine also holds that the meaning publicly given by contemporary or long professional usage is presumed to be the correct one, even if the language may have a popular or an etymological meaning that is very different.

For example, let's say that a law was passed in 1920 that prohibited the sale of alcohol. If someone were to challenge the law's meaning today, a court would likely look to the contemporaneous exposition of the law at the time it was passed. This might include looking at how the law was interpreted and enforced by law enforcement officials and the courts at the time.

Another example might be a contract that was signed between two parties in 1990. If there is a dispute over the meaning of a particular clause in the contract, a court would likely look to how the clause was interpreted and applied by the parties at the time the contract was signed.

These examples illustrate how contemporanea expositio can be used to determine the correct interpretation of a statute or document. By looking at how the language was understood and applied at the time it was enacted or signed, courts can arrive at a more accurate understanding of what the law or contract was intended to mean.