You will be given a definition of a task first, then some input of the task.
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.

The Polish – Lithuanian Commonwealth ( or Union , after 1791 the Commonwealth of Poland ) was a state of Poland and Lithuania ruled by a common monarch .
Output:
The Polish – Lithuanian Commonwealth – formally , the Crown of the Kingdom of Poland and the Grand Duchy of Lithuania and , after 1791 , the Commonwealth of Poland – was a dual state , a bi-confederation of Poland and Lithuania ruled by a common monarch , who was both King of Poland and Grand Duke of Lithuania .