Conversion (gridiron football)
The try (American football, also known as point(s) after touchdown, PAT) or convert (Canadian football) is one scrimmage down played immediately after a touchdown during which the scoring team is allowed to attempt to score one extra point by kicking the ball through the uprights in the manner of a field goal, or two points by bringing the ball into the end zone in the manner of a touchdown; depending on league rules, one point may also be scored by manner of a safety.
If the try or conversion is scored by kicking the ball through the uprights, the team gets an additional one point for their touchdown, bringing their total for that score from six points to seven. If two points are needed or desired, a two-point conversion may be attempted by running or passing from scrimmage. A successful touchdown conversion brings the score's total to eight.
Whether a team goes for one or two points, most rules regarding scrimmage downs, including scoring touchdowns and field goals, apply as if it were a normal fourth down play. Exceptions, including cases where the defense forces a turnover during a conversion attempt, vary between leagues and levels of play.
The try/convert is among the oldest parts of the game of gridiron football and dates to its rugby roots. In its earliest days, scoring a touchdown was not the primary objective but a means of getting a free kick at the goal (hence why the name "try," more commonly associated with rugby today, is still used in American football rule books), and thus early scoring rubrics for the game gave more points to the subsequent kick than the actual advancement of the ball into the end zone. The related term "conversion" is still used in both rugby union and rugby league to refer to extra points scored by kicking the ball through the posts after a try has been scored.
By the start of the 20th century, touchdowns had become more important and the roles of touchdown and kick were reversed. By this time the point value for the after-touchdown kick had reduced to its current one-point value while the touchdown was now worth five. (This later increased to six points in American football in 1912 and in Canadian football in 1956.)
Although a successful kick is only worth one point, missing one can decide the outcome of the game. Perhaps the most famous example to this was the 2003 game between the New Orleans Saints and Jacksonville Jaguars where, after scoring a touchdown as time expired as a result of the multiple-lateral River City Relay, Saints kicker John Carney missed the extra point, giving the Jaguars a 20-19 victory and eliminating the Saints from playoff contention. On November 11, 1979 the New York Jets lost to the Buffalo Bills 14-12 - the difference coming from two missed extra points by place kicker Toni Linhart. Linhart never played another game in the NFL.
Another 2003 game, this one between the Carolina Panthers and Tampa Bay Buccaneers, was sent to overtime after what would have a game-winning extra point was blocked; the Panthers won the game in overtime 12-9. A 2005 game between the Green Bay Packers and Tampa Bay Buccaneers is another notable exception, as the Buccaneers won 17-16, the difference being Ryan Longwell missing an extra point after a Packers touchdown.
Duration of the play 
In the NFL and American high school football (in most states), the play is over once either the ball becomes dead or the defense takes possession. In many other levels of football, including the Canadian Football League and American college football, the play continues after a turn-over to the defense. This allows the defense to return the ball to the opponent's end zone for two points and also allows for a one-point safety. Two states, Texas and Massachusetts, play high school football under NCAA rules and thus allow the defense to score on an extra-point attempt.
Differences between leagues 
In the National Football League, the scrimmage for point after attempt takes place from the two-yard line. In American high school and college football, it is from the three-yard line. In Canadian football it is from the five-yard line. The game clock does not run during an extra-point attempt, except for some rare circumstances at the high-school level (some state associations allow for the clock to run continuously in the second half if one team is leading the other by a large margin) and for arena football, which runs the clock continuously except during the final minute of each half.
In the NFL, the conversion is required after a touchdown scored during the regulation game (i.e., not overtime), because point differential is used for some tiebreakers in the standings. Rarely, this can result in such an attempt having to be made at the end of the game when it cannot change the outcome of the game; one of the best-known examples of this occurred after the winning touchdown by the Philadelphia Eagles in the December 19, 2010 game known as the Miracle at the New Meadowlands.
If the game is in sudden death overtime, the extra-point attempt is omitted if the winning score is a touchdown. In American high school and college football, it's likewise omitted following a touchdown on the game's final play if six points were enough to win or if the scoring team was already ahead or can not win or tie the game with a successful conversion attempt.
There is, however, one notable exception in college football because the defense can also score two points on a return of a conversion try (and theoretically score a one-point safety) and the NCAA rules state that the conversion try must be run if any scoring in it could impact the outcome of the game. Therefore, if a team scores to take the lead by one or two points as time expires, they must still attempt the conversion, although most teams will simply opt to take a knee to prevent the risk of the defense scoring. For example, on October 24, 2009, Iowa scored as time expired to take a 15-13 lead over Michigan State. Making the conversion would have made no difference in Iowa winning the game, but Iowa still had to attempt it, so Ricky Stanzi simply knelt down, as a return by Michigan State would have tied the game and forced overtime.
In Canadian football, the scoring team is entitled to a conversion play after scoring with no time on the clock, but may choose to waive it if they feel it's not needed. Because head-to-head points scored is used as a tiebreaker in the standings between teams, they often choose to take it if is against a division opponent with whom a tie in the standings is possible.
Other leagues 
In 1968, the AFL and NFL eliminated the extra-point kick for interleague preseason games, only allowing one-point scrimmage plays. The World Football League and XFL did the same in their short lives, though the XFL later implemented a variable system that allowed increasing point values for increasing the distance to the end zone on the attempt for its playoffs; said system was later adopted by the Stars Football League and, in a reduced form, the Lingerie Football League. In arena football, two points can also be scored by means of a drop-kicked field goal. Some youth football leagues turn the scoring upside-down to an extent, scoring one point for a running touchdown and two points for either a passing touchdown or field goal; six-man football follows a similar convention that rewards one point for a pass or run and two points for a kick.
See also 
- American football
- Comparison of Canadian and American football#Points after touchdown
- Glossary of American football
- "Tampa Bay Buccaneers at Green Bay Packers — September 25th, 2005". Pro-Football-Reference.com. 2005-09-25. Retrieved 2012-11-23.