The Vienna Convention on the Law of Treaties (1969) defines a treaty in Article 2 as “an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument, or in two or more related instruments and whatever its particular designation.”
Treaties can be bilateral (between two countries), multilateral (between three or more countries) or plurilateral (between one state and a group of states).
In Canada, treaties fall into one of two categories: those that do not require new legislation in order to be implemented and those that do. For treaties that don’t require legislation, the Canadian government will wait at least twenty-one sitting days after a treaty is tabled and then begin the process of bringing the treaty into force. For treaties that do require legislative changes, the Government will generally wait a minimum of twenty-one sitting days before introducing the necessary legislation, although exceptions can be made if a treaty needs to be urgently ratified. (For more information on the process see https://treaty-accord.gc.ca/procedures.aspx?lang=eng.)
For example, the Convention for the Suppression of Unlawful Seizure of Aircraft, signed in The Hague in 1970, is a multilateral treaty of which Canada is a signatory. Canada signed the Convention on December 16, 1970, but did not ratify it until June 20, 1972. The legislation was tabled in the House of Commons on June 23, 1972 and the Convention came into force in Canada on July 24, 1972. (The in force date differs greatly by country.)
The Canadian Treaty Series is available at https://www.treaty-accord.gc.ca/cts-rtc.aspx and you can search Canada’s treaties at http://www.treaty-accord.gc.ca/search-recherche.aspx.