I've noticed that many, not all, scripts often use the double hyphen (--) to combine two ideas in a single sentence such as: 'She looks behind her -- but he's not there'.  I take it this is done for dramatic effect but it still strikes me as odd since I don't believe it to be proper usage.  I know it doesn't replace the standard single hyphen such as when breaking up a compound word like 'hell-raiser' but then I'll see it used in place of elipses (...) often in a passage of dialog to indicate a beat or pause.  Some scripts use both hyphens and elipses in dialog.  Is there a difference?  Is one meant to be stronger than the other?

Thanks in advance.

A double hyphen is used when someone's dialogue is suddenly interrupted.

JOHN picks up a gun

     JOHN
I wondered if it's loaded--

BLAM!


The elipses (...) is used when the dialogue drags off.

MOM enters the kitchen.  There's spaghetti sauce everyone.

    MOM
Oh dear...



Phil

Phil's usage above is correct, but I see it isn't what you're referring to.

The double hyphen (which in English usage is referred to as a dash, not a hyphen, because it is longer) is used in English to present an "aside" in a sentence. It's used like a colon or semi-colon or parenthesis are used. Basically to present a break in the though process to present something else, but belongs in the actual flow of the sentence and may or may not present a complete thought.

Therefore, I could have just as easily written: The double hyphen--which in English usage is referred to as a dash, not a hyphen, because it is longer--is used in English to present an "aside" in a sentence. Space or no space? The jury is out on that one, and it can go either way.

Actually I was referring to both so thanks George and Phil.  Now--as you can see by this hair-raising example--I know when to use my elipses, hypens, dashes...

BTW, it seems like standard keyboards don't even have a dash key.  Strange.  I guess that's why we double hyphen our dashes.

Quoted from mgj BTW, it seems like standard keyboards don't even have a dash key.  Strange.  I guess that's why we double hyphen our dashes.

That's exactly why we use a double hyphen. It's to simulate the dash. Some Word Processors (like Word) will automatically change the double hyphen to a dash, since it is in the character set of most fonts, if you know the ASCII code for it.