In a parliamentary system, the largest of the opposition parties, given a special role to play in the legislative process.

  In a parliamentary system, the members of parliament who do not support the government are known collectively as the opposition.  The largest party grouping of these members is often given formal recognition as the official opposition, with its leader known as the leader of the opposition.  This recognizes the opposition as a potential alternativ [..]

The party or coalition of parties holding the second largest number of seats in the House. It is accorded certain financial and procedural advantages over other parties in opposition

The political party that had the second most Members of Parliament elected in the election.

The party with the second highest number of members elected. It is their job to study government legislation, politics and programs and offer alternatives.