Within. Unfortunately, in real life this has a significantly different meaning to what it does in-game. I imagine this is probably worse in translation, unless the new language has separate words for the two meaning, and they are applied correctly - but it's bad enough for you lot out there, it seems. Of course, by 'you lot', I primarily don't actually mean my readers, but if this proves a valuable resource in demonstrating internet folly (of which there is much) then I consider it a job well done.
Normally, if I say something is 'within' something else, you take it to mean in it's entirety. Such as "the phrase was within quotation marks."
In 40k, however, this is not actually the case. In 40k, the word 'within' means 'the difference between two points'...and it always has.
I've seen a little bit of e-raeg recently over the fact that when you disembark only the merest fraction of your base needs to be 2" away from the door...yet people seem to have no issue when their models are assaulting something 6" away...or measuring ranges. For something to be 'within' range, it needs to be equal to or less than the maximum range away from the base or gun barrel, depending on unit type. There is NO DIFFERENCE when measuring other distances, be they Coherency, assaulting, movement or disembarkation. [Cheating with movement, one of the very sadly rampant 'accidents' in our Hobby, is no worse than saying something is in range to be shot when it clearly isn't.]
I am fully aware that the ability to disembark fully 2" away from the vehicle essentially gives you an extra inch of movement and so are GW. If you actually *look* at the diagram of it in the BRB, it clearly shows a Marine leaving a Rhino from that distance - and it is true in reverse, too - you can get into a vehicle from that far away (though I doubt the kind of players who whine about rules they perceive to gyp them would be so conscientious as to ensure ALL of a squad can get within 2" of a door before removing them and declaring they are aboard...)
If it helps you, think of it this way. People in real life do not have a base. They *do* however, have personal space, to an extent. No one in reality stands right in front of, or beside a stranger or non-intimately known sort of person - consider this the area the model's base in our analogy.
If you are on a bus, you no longer have that, when the bus is full. Strangers will sit beside you, as will acquaintances. Fact is, that's where the seats are. In 40k, those Transports cannot carry half the models they are meant to, because of stupid scaling. Imagine, then, that they are fairly tightly packed in there, too.
When you get off the bus, this personal space 'appears' again, and people you don't know will not be crowding you, as long as the space exists for them to not be crowded themselves. Indeed, a lot of people jump off buses' last step, or speed up at least, to create this 'bubble' all the quicker. Is it unrealistic then, for GW to put this into effect in rules?
Plus, of course, if you go back to earlier Editions, it has always been the wording, and 'within' has always meant the same, in 40k terms. Just because it 'wasn't played that way' is irrelevant. Wrong is wrong, and populism doesn't make it right.^
If you fail to interpret the rules correctly once, and they don't change, you are likely to take offence when it is pointed out to you they were always that way. Don't. It's not an insult, just because your reading comprehension isn't what you think it is. The fact that so many of us start the Hobby as kids is kinda a bad thing, reinforcing this culture of 'Don't read the Rulebook yourself! Learn by playing other people!', which perpetuates the same mistakes time after time.
Learn the Rules by Reading the Rules. Learn the Game by Playing the Game. Two independent processes.