The first patent application for an invention establishes the priority. If you apply to patent the same invention in other countries within 12 months, these form a patent family.

Here is a more precise definition of the terms priority and patent families:

The priority period starts with the application to patent your invention in Switzerland or in another member state of the Paris Convention or the World Trade Organization (WTO). You have only 12 months to apply to patent the same invention in other countries. However, you can claim the priority date of the first application for these subsequent applications. This means that for these additional applications, this priority date will be respected in evaluating the novelty of the invention.

The technical documents of the first patent application are the priority documents. A group of patent documents relating to the same priority documents are known as a patent family. As there can be different changes to the original text in the various national patent grant procedures, the claimed scope of protection of the individual patent family members are not always the same. However, it is in principle the same invention.