This post will explain what is meant by the terms “a parliament”, “a session” and “a sitting”.
A parliament can refer to an institution, e.g. the Parliament of Canada, but it also refers to the period of time during which the institution of Parliament exercises its powers. A parliament, at least in the UK and Canada, does not exceed five years. A parliament begins with the proclamation of the Sovereign (UK) or Governor General (Canada, Australia, New Zealand, etc.) calling for the formation of a new Parliament and setting the dates for a new election and the day the new Parliament will first meet. A Parliament ends with the proclamation announcing its dissolution.
As stated, traditionally and constitutionally, a Parliament does not exceed five years. Some legislatures have introduced fixed-term election legislation which sets the life of a parliament at four years. A parliament can end before the four or five year limit, however. If the government of the day loses the confidence of the House, and no other government can be formed to take its place, the parliament will be dissolved. This happens most frequently during times of single-party minority government.
A session is a period of time between the summoning of a Parliamentand its prorogation. How many sessions are there during the course of a single Parliament? That can vary. Some legislatures prorogue regularly, every fall or spring. The UK Parliament prorogues every spring, usually in May, and begins a new session a couple of weeks later. In Canada, the federal Parliament does not follow this tradition; consequently, there is no set length for or number of sessions during a single Parliament. The number of sessions have ranged from one to seven. Each new session begins with a Speech from the Throne.
During each session of Parliament, there are a number of sittings. The Standing Orders will usually provide the times and days for the sittings of a legislature. For example, the Canadian House of Commons normally sits five days a week (but not every week) as follows:
It is important to note, however, that a sitting does not necessarily equal a calendar day. There can be two sittings in a single day, or a single sitting can last more than one day. To extend a sitting, the House has to agree to a motion to do so. These motions can be moved by Ministers as well as Members. Similarly, sittings which last more than one day are rare, and occur mainly as the result of events such as filibustering by the opposition parties; a motion to extend the sitting beyond the normal adjournment in order to consider a specific item of business; to continue an emergency or take-note debate past the normal hour of adjournment; to complete all remaining stages of a bill, or to allow all Members wishing to do so to speak on an item; and to hold recorded divisions at the report stage of a bill.
To summarize, a single Parliament will have or one or more sessions, and each session will have a number of sittings.