American football looks impenetrable from outside: armoured men who stand still, then collide, then stand still again, while a clock that says fifteen minutes takes an hour to run down. It is actually a simple game with a lot of vocabulary. Here is the whole thing, from nothing.
The object is to move an oval ball to the far end of the field. The field is a rectangle marked with a line every five yards. Between the two goal lines it is a hundred yards long, and beyond each goal line there is a ten-yard area called the end zone. Each team has eleven players on the field at a time.
The one rule everything hangs on
The team with the ball gets four attempts - called downs - to advance it ten yards. If they manage it, they get a fresh set of four downs from where they reached, and may keep going indefinitely. If they fail, the other team takes possession where the ball stopped.
That is the whole engine of the sport. Everything else is a consequence. It is why play happens in short bursts with a pause between them, why there is time to call a specific play, and why coaching matters so much. A commentator saying "second and seven" means it is the second attempt and seven yards still need to be gained.
Scoring
A touchdown is worth six points and is scored by carrying the ball into the opponents' end zone or catching it there. After a touchdown the scoring team gets one extra attempt: a kick through the posts for one point, or a single play from close range for two.
A field goal is worth three points. It is a kick through the posts from open play, usually attempted on the fourth down when the team is close enough to have a chance but too far out to be confident of gaining the yards. A safety is worth two points and goes to the defending team when the attacking team is tackled behind its own goal line.
The fourth-down decision
Fourth down is where the game gets interesting, because a team has three choices. Go for it, and risk handing the opposition excellent field position. Kick a field goal, if close enough. Or punt - kick the ball away deliberately, giving up possession in exchange for pushing the other team a long way back.
Punting looks defeatist to newcomers and is usually correct. Field position is a real currency in a sport where you have to earn ten yards at a time.
Nothing in American football makes sense until you accept that giving the ball away on purpose, from a good position, is frequently the smart play.- PuroGoal
Who is on the field
Substitution is unlimited, so teams field entirely different units depending on the situation. The offence is the group that plays when the team has the ball; the defence plays when it does not; and the special teams handle kicks.
On offence the quarterback receives the ball at the start of each play and either hands it to a running back, throws it to a receiver, or runs. Five offensive linemen protect him and open gaps for runners. On defence, the defensive line tries to reach the quarterback, linebackers cover the middle ground, and cornerbacks and safeties defend against passes.
The ball may be thrown forward only once per play, and only from behind the line where the play started. That single restriction is what separates American football from rugby, and it is why the formations look the way they do.
Losing the ball
There are two ways to hand possession over by accident. An interception is a forward pass caught by a defender. A fumble is a ball dropped or knocked loose while a player is carrying it, which either side may then recover. Both are called turnovers, and both tend to decide matches.
Why the clock behaves like that
A match is four quarters of fifteen minutes. It takes around three hours. The clock stops when a pass falls incomplete, when a player goes out of bounds, after a score, during official reviews, and for television breaks - which is most of the reasons.
This produces one of the sport's best features: the end of a close game, where a losing team uses the sidelines and its remaining timeouts to stop the clock and squeeze an extra minute of football out of thirty seconds, while the leading team tries to keep the ball in bounds and let it run. It also produces the kneel-down, where a winning quarterback deliberately drops to the ground to burn time, which looks like bad sportsmanship and is simply arithmetic.
Penalties
Officials throw a yellow flag onto the field when a rule is broken, and the punishment is measured in yards rather than in time or cards. Common ones are holding (grabbing an opponent illegally), offside (crossing the line before the play starts) and pass interference (illegally impeding a receiver before the ball arrives). The team that was fouled can usually choose whether to accept the penalty or take the result of the play instead.
Where to start watching
Pick one team and follow it for a season; the sport rewards familiarity far more than it rewards neutrality. Watch the down and distance marker on screen before each play rather than the ball - it tells you what the attacking team is likely to try. And give it three or four matches before deciding. Almost everyone who dislikes American football dislikes it for the first two, which is fair, and then it clicks.
