In American football, a turnover on downs occurs when a team fails to convert a fourth down into a first down by gaining the required yardage. A team has four chances (each chance is called a "down") to gain ten yards or to score. Any ground gained during one down short of these ten yards is kept for the next chance. Thus, if a team gains four yards on first down, it then has three chances to gain the six remaining yards. If a team gains the required ten yards, it receives another four downs to gain another ten yards (an event called a "first down") or cross the goal line for a score.