Article 3 of the treaty is normally the article that deals with general definitions for the treaty.
It normally includes the definition of the country. This includes the geographical area that is covered. Canada normally will include the sea and air space as well as the continental shelf. Other countries, such as Armenia, will define the geography to include internal waters.
It is important to check the definition of person in the treaty – while it will always include individuals, you need to check which other organizations are included.
This paragraph also usually includes a definition of the competent authority. The competent authority is the government body that you need to contact to resolve a treaty conflict such as both countries considering you to be resident in their country (see more on this next week).