Session is the word used to describe the Parliamentary year. A session begins with the State Opening of Parliament, pre-2012 this usually ran from November to November. From 2012 this occurs in the spring. Sessions run for 12 months as the general election will generally happen on the first Thursday of May every 5 years.
The session used to run for 12 months unless there was a general election. If a general election took place, the session increased in length to include the additional months from the new date of the State Opening which took place shortly after the election.
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Related glossary term: Parliament
Related glossary term: Prorogation