In First Past the Post assemblies, where the tendency to gravitate into two major parties or party groupings operates strongly, government and opposition roles can go to the two main groupings serially in alternation. In this context, the opposition forms a recognised, even semi-official "government-in-waiting". Its "opposing" can degenerate into a charade pending the eventual exchange of roles and occupation, or reoccupation, of the Treasury benches.
The more proportional a representative system, the greater the likelihood of multiple political parties appearing in the parliamentary debating chamber. Such systems can foster multiple "opposition" parties which may have little in common and minimal desire to form a united bloc opposed to the government of the day.
Some well-organised democracies, dominated long-term by a single faction, reduce their parliamentary opposition to tokenism. Singapore exemplifies a case of a numerically weak opposition; South Africa under the apartheid regime maintained a long-term imbalance in the parliament. In some cases tame "opposition" parties are created by the governing groups in order to create an impression of democratic debate.
By their very presence in the debating chamber, parliamentary oppositions recognise the legitimacy of the system of politics, and thus may share many of the views of the government. The opposition in such cases can justly claim the title of His/Her Majesty's Loyal Opposition.
The title of "Official Opposition" usually goes to the largest of the parties sitting in opposition with its leader being given the title "Leader of the Opposition".