I took some quotes in order to make explaining easier:
Rachel: I don�t know, I don�t know. Look, maybe we should take a break.
Ross: Okay, okay, fine, you�re right. Let�s ah, let�s take a break,
(goes to the door) let�s cool off, okay, let�s get some frozen
yogart, or something.. (opens the door)Rachel: No. (Ross is standing in the doorway.) A break from us.
~**~ Rachel broke up with Ross. A break is a break. To take a break means you have broken up...as you can see from below evidence. -----
Chandler: So, what are you doing here? I thought tonight was your big anniversary dinner.
Ross: Yeah, little change in plans. Ahh, we�re gonna break-up instead.
(Chandler and Joey stare at each other in shock.)
~**~ Ross thought(rightfully so) that he had broken up with Rachel. -----
Mark: Rach, are you okay?
Rachel: (on the verge of tears) Yeah, I�m fine.
Mark: You wanna talk, I mean I can come over?
Rachel: No! Really, no, please, please, that�s, that�s okay.
Mark: All right, all right, I�m coming over, and I�m bringing Chinese food.
~**~ This mess is also partly Mark's fault. He forced his so called friendly help on Rachel. ----
Chloe: Still no smile?
(She kisses him. Ross leans back for a second, and then they both kiss, more passionately this time.)
~**~ Chloe is also at fault. She initiated the kiss on the clearly drunk Ross. --- Monica: How�s the big anniversary dinner?
Rachel: Well, we never actually got to dinner.
Monica: Ohhh, nice.
Rachel: No, we kinda broke up instead.
~**~ Rachel explicitly confirms that they "broke up." (in the future she will not be able to admit that she was wrong) ---- Ross: Listen. Oh hey, hey, the important thing was that she meant, she meant nothing to me!
Rachel: And yet she was worth jeopardising our relationship!!
~**~ There was no more relationship. They broke up. ---- Ross: Look, I didn�t think there was a relationship to jeopardise. I thought we were broken up.
Rachel: We were on a break!
Ross: That, for all I knew would, could last forever. That to me is a break-up.
Rachel: You think you�re gonna get out of this on a technicality?
Ross: Look, I�m not trying to get out of anything, okay. I thought our relationship was dead!
~**~ Here Rachel says its a technicality but in the quotes before she clearly says they broke up(talk about being redundant). ----
Ross: Look Rachel, I wanted to tell you, I thought I should, I-I did, and then Chandler and Joey convinced me not to.
~**~Chandler and Joey...sure gave some bad advice...Honesty is the most important thing in a relationship and I give Ross props that he was willing to tell Rachel the truth about sleeping with Chloe.
----
Ross: Don�t you realise none of this would�ve ever happened if I
didn�t think at that same moment you weren�t having sex with
Mark?Rachel: All right. Let�s say I had slept with Mark. Would you have
been able to forgive me?
...
Ross: (covering his ears and screaming) La-la-la-la-la-la-la-la-la-la!
Okay, okay, yeah, I would have been devastated but, I would
still want to be with you. Because it�s, I mean it�s you.~**~ "I mean its you"----how sweet :)
----
Ross: What, now you�re not even talking to me? (moves over to the
coffee table) Look Rachel, I-I�m sorry, okay, I�m sorry, I was
out of my mind. I thought I�d lost you, I didn�t know what to
do. Come on! Come on, how insane must I have been to do
something like this? Huh? I-I don�t cheat right, I, that�s not
me, I�m not Joey![Cut to Monica's bedroom]
Joey: Whoa-ho-ho! (He looks at Chandler, who gives him a �come on� look.) Yeah, okay.
~**~Joey underlines the fact that he's a cheater(even though we only have
evidence of him cheating 2 or 3 times).
-----
Ross: Look, look, there�s got to be a way we can work past this. Okay,
(takes a hold of one of her arms.) I can�t imagine, I can�t
imagine my life without you. (Both of them are starting to cry.)
Without, without these arms, and your face, and this heart. Your
good heart Rach, (drops to his knees and hugs her around her
waist) and, and....~**~ I cry at this moment every single time...so heartbreaking to watch.
David Schwimmer and Jennifer Aniston were absolutely wonderful in this
episode. Great acting!
----
Rachel: (crying) No. I can�t, you�re a totally different person to me
now. I used to think of you as somebody that would never, ever
hurt me, ever. God, and now I just can�t stop picturing with
her, I can�t, (Ross stands up and backs away) it doesn�t
matter what you say, or what you do, Ross. It�s just changed,
everything. Forever.~**~ What about Rachel hurting Ross? They love each other and they should have worked things out in my opinion. Marriages survive things like these...i think that they could of also and they aren't married.