Complex sentence: The two-round system (also known as the second ballot, runoff voting or ballotage) is a voting system used to elect a single winner where the voter casts a single vote for their chosen candidate.
Split into simpler sentences: The two-round system (also known as the second ballot, runoff voting or ballotage) is a voting system used to elect a single winner. Under the two round system, the voter casts a single vote for their chosen candidate.