Cohabitation in government occurs in semi-presidential systems such as France when the President and the Prime Minister come from different political parties. It is seen as a double-edged sword. It prevents the stagnation of "split majorities" that can occur in Presidential systems - a concern especially relevant to the French in light of instability and political paralysis - yet it can also result in massive political tension in times of crisis, as seen in Sri Lanka during the later months of 2003. (Source: " class="external">http://news.bbc.co.uk/1/hi/world/south_asia/3256649.stm)
The term is also used for a couple living together without being married. See also: Concubinage.