When Tybalt tries to rile Mercutio into fighting him he says "Thou art consortest with Romeo!". This is not the original line and makes no sense! The way he said it means "You are consort with Romeo." What he should have said was either "Thou art consorting with Romeo" or hey! The original line: "Thou consortest with Romeo."
1st) Which adaptation are you talking about?
2nd) If you mean the Baz Lurhman (forgive the spelling) piece, he edits and cuts many lines. I don't know how many Zepherelli edits but I know Baz edits a lot.
Well, you might notice that not all the lines in the novel are used in the movie. I've got the unabridged Romeo and Juliet by William Shakespeare and when I'm not drooling over Leo I'm following the lines. They switched the order of the lines, they shortened a lot of the big, long sonnets, they changed words sometimes. Just let it go.
If you've ever read the original version you'd know that they got rid and modified 85% of the words for this movie, as some of the words no longer are used. This isn't a slip up.
I think this slip-up should stand. Of course tons of lines were cut from this flick, but it seems Luhrmann got a bit scissor-happy with this particular line of the Bard's. Like 'Anonymous' pointed out, this line now makes no sense whatsoever, for the sake of one word.
Baz did a much better job on this movie than i thought he would, infact i expected him to BUTCHER it. but yea, he did ruin a few awsome lines, "Thou Art Consortest With Romeo" was just a maor screw up. and yea, it was a play. a novel is like Bridge to Tereabithia or somthing.