A few of you out there may be confused as to why soccer's 90-minute clock doesn’t stop during injuries, and why there’s three or four extra minutes tacked on to the game.

It all has to do with how the sport handles breaks in play, which we’ll call by their proper name: stoppages in play. A stoppage in play is just that: when play stops for whatever reason, like a substitution or an injury. The rules are loose and leave a lot up to the referee’s discretion, so keep that in mind moving forward.

The short of it is instead of stopping the play clock like in basketball or American football, referees calculate the amount of time when play stopped during each 45 minute half and tack it on to the end of that half. That extra time is referred to as “stoppage time,” but is referred to by FIFA as an “allowance for time lost.”

In reality, it’s far more complicated than that. Referees essentially have complete discretion as to how much stoppage time is added to the end of each half. Law 7 in FIFA’s Laws of the Game outline what justifies an allowance: “substitutions; assessment of injury to players; removal of injured players from the field of play for treatment; wasting time; any other cause.”

Those last two give the referees a lot of discretion as to what to count toward the allowance at the end of the half. The Laws of the Game go on to say that an allowance should only be made if the stoppage in play is beyond the normal pace of the game.

“Many stoppages in play are entirely natural (e.g. throw-ins, goal kicks). An allowance is to be made only when these delays are excessive,” the Laws of the Game read.

So if a ball is kicked out of bounds but play resumes within 20 seconds without an unncessary delay, the referee will simply let it play out. The freedom to add time counters a team’s ability to waste time. If team A is up a goal and the 90-minute game clock never stops, the team could run the clock down by faking injuries or taking too long to throw a ball in from out of bounds.

The “fourth official” is responsible for calculating how much stoppage time is added to the clock. There are some unwritten rules, one of them being a substitution counts for 30 seconds of stoppage time, but if a player is clearly taking his sweet time, then more time can be added.

Yet it doesn’t really end there either. A referee is allowed to add as much additional stoppage time to the game on top of what he already added if further stoppages in play happen during the extra allowance.

Even further, he can allow a team to finish out an “attack” or a play on the goal if he deems it appropriate. So if Team A is up by one goal in the last 10 seconds of stoppage time and Team B is moving the ball in scoring position, the referee can let that play out.

Does it create a sort of grey area in the rules? Yes. Does it cause controversy? You bet. For examples, see Football Bible's explanation of stoppage time.