Can someone explain offsides to me? Thanks.
It depends. Are you female? 
No, but I was watching the womens’ NCAA finals and one team had two goals disallowed for being offsides. They showed a replay and I just didn’t understand.
You’re offside (not “offsides”) if the ball is played forward to you and there are fewer than two defenders between you and the goal. Exceptions apply to throw-ins and, since by definition it is taken at the goal-line, a corner. The basic idea is to prevent one or more strikers camping permanently by the goal and waiting for the ball to be hoofed downfield to them.
Thanks, Malacandra. That makes perfect sense.
Does the goal keeper count as one of the defenders?
Yes. Also, the relevant time for determining offside is when the ball is played to you, not when you receive it, so you can be well behind the defense when you actually receive the ball as long as you were onside when the ball was passed.
I have to receive the ball for the call to made though, right? If someone passes me a ball while I’m offside but the pass is intercepted will there still be a call?
I was watching some soccer game at a friends house. Their grade school daughter is on a soccer team and is very into it. She saw a ball make contact with someones hand, which the official was blocked from seeing, so a handball (?) wasn’t called. She saw it though, and screamed, “that was a handjob!!!” We adults tried so hard not to laugh.
Ha. It’s amazing that you’ve managed to cut right to the heart of the rule in so few words. The rule there is a complicated and sometimes controversial one. The player receiving the ball has to be involved in “active play,” I think the term is, which can mean either that she’s physically receiving the ball, or that she’s interfering with the defense’s ability to defend, or doing something that’s providing an advantage for her team thanks to her offside position. So if you’re just standing there, theoretically, no offside. If you fake a run down the sideline (which I’m supposed to say touchline but USA! USA!) and draw a defender while another onside teammate runs and picks up the ball, offside.
So in the case of the pass that gets cut off, the advantage is probably to the defending team, so no whistle.
Former ref here, lifelong adherent of the beautiful game, and I can tell you this should not be called offside. Some refs with a poor understanding of the rule might call it that way, but the interference with the defense is meant to be much more direct, such as screening a shot or playing at a ball without touching it. Merely making a run away from the play is not sufficient to be called for offside, whether the defense responds or not. Pulling defenders out of position is just good tactics.
As mentioned, you need to be involved in the play to have offsides called; so if your teammate (who started onsides) intercepted the pass, then the referee would need to decide whether you were involved in the play, by distracting a defender or something.
If a defender intercepted the pass, another rule would come into effect, which is that the referee can choose to not call a foul if they think stopping play would help the fouling team. So if the goalie grabbed a pass to you when you were offsides, the referee would probably not call the offsides, as the defending team is in at least as good a position with the goalie having the ball as they would be if the ref called offsides and gave the defence a free kick.
Thanks. That’s a better explanation.
Which brings us to perhaps the most famous quotation on the subject, by Bill Shankly:
You can only be offside in the opposition’s half, too.
Here is a link to the FIFA Laws of the Game (pdf!): http://www.fifa.com/mm/document/affederation/federation/81/42/36/lawsofthegameen.pdf
Here is a link to an interactive guide to offside: http://www.fifa.com/flash/lotg/football/en/flash/start.html
As I used to teach new referees: You have to do two things, 1) identify offside position, 2) determine “active play.”
The position part is easy: opponent’s half, ahead of the ball, past the next to last defender. Note: you are past the next to last defender if any part of your body other than your arms is closer. A lot of times, people howl over supposedly onside players when, while their feet were onside, their head or shoulders were not.
The “active play” part is harder, though FIFA has made this clearer now:
Why do American posters pluralise the term? Does MLS actually call it offsides? Do commentators call it offsides in the US?
They don’t - the OP did but I don’t believe it’s standard. It was corrected in post #4. I don’t think that the OP meant to pluralize, I suppose he/she was thinking of it in analogy to ‘besides’ or something like that.
This is easier than determining ‘active play’ in the sense that it does not require interpretation, just plain observation. That said, I don’t think determining offside position is exactly easy because you need to do it at exactly the moment that the ball is kicked, which means you have to keep your eyes on two things at the same time: the attacker’s position in relation to the defenders, and the position of the ball. I’d say that is actually pretty hard.
Well, it’s no piece of cake, I can tell you, having been an official in the professional game! :eek:
But in general you don’t try to look at two things at lower level soccer; you listen for the kick of the ball when the attack is a long pass, while watching the potentially offside attackers, much like a baseball umpire listens for the ball hitting the glove while watching the foot hit the bag. Of course, even that isn’t easy, since they aren’t exactly standing still during the process. Fuckers move FAST, let me tell you! And if you’re a professional ref’s asst. in front of a big crowd, you may not have the luxury of hearing the ball played long over the noise of the crowd! 
Actually, sadly, most Americans do call it offsides. It’s because we misuse the term in American football regularly, and to some extent in hockey, too. I’ve never understood how you can be off more than one side at a time. <lol>
As well as when you are in your own half of the field at the time the ball is played to you.