instruction:
In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
question:
A federation is a union of a number of self-governing states or regions , which are joined together under a central government .
answer:
A federation ( also known as a federal state ) is a political entity characterized by a union of partially self-governing provinces , states , or other regions under a central federal government ( federalism ) .

question:
During the American Civil War , the river , with few convenient fords and fewer bridges , provided a barrier and defensive line .
answer:
During the American Civil War , the river , with few convenient fords and fewer bridges , provided a barrier and defensive line behind which movements of troops could be accomplished with little fear of attack from the river-side flank .

question:
A card game is any game played with playing cards .
answer:
A card game is any game using playing cards as the primary device with which the game is played , be they traditional or game-specific .