Where is the pawn break?

I'd like to better identify pawn breaks.

"A break move is a pawn move that breaks up the opponents fixed pawn chain by attacking the opponent's pawns with that pawn. In his classic work Pawn Power Chess, Hans Kmoch calls this move a liberation lever." - Dan Heisman

In this first example, the pawn break occurs at 8...c5.

In the second example with the Sicilian-Scheveningen opening I see pawn pushes on the kingside, and a  little on the queenside, but on what moves are the breaks happening? Thanks!

The Sicilian - Scheveningen

Themes for White: Pressure on the d file, space advantage, e4-e5 break (often prepared with f2-f4), f2-f4-f5 push, g2-g4-g5 blitz (see Keres attack).

Themes for Black: Pressure on the c file, minority attack (and counterplay in general) on the queenside, pressure on White's pawn on e4 or e5, d6-d5 break, e6-e5 transposing into the Boleslavsky hole.

i think the only real  break moves in the Sicilian  game were d4 and b5

What about 19.fxe6? White is attacking with a pawn and breaking up Black's pawn chain. Isn't that what a pawn break is?

I would agree with Musikamole: I think that if there is a pawn break to be categorized, it is move 19. Black's move 3 taking the d pawn is not really a pawn break as he is initiating this from his own chain. Even at move 19, we do not have long pawn chains that are typically the subject of pawn breaks.

"A break move is a pawn move that breaks up the opponents fixed pawn chain by attacking the opponent's pawns with that pawn."

Using that definition I'd say that 16. f5 is the pawn break.

Thanks for the response. So, the break move is not the capture (19.fxe6) that breaks the pawn chain but the pawn push (16.f5) that threatens to break up the pawn chain of the opponent?

I know this must sound nit picky, but I'd like to know what move an IM or GM is referring to when talking about pawn breaks.

Yeah, I think so but it's not important to know the ins and outs of every term. I often see beginners/improvers discussing the exact nature of things I've never even heard of in 36 years of play. Of course, I understand the concepts, just never knew half these things have proper names. I think playing is much more important than the classification and dissection of minute details.

Now that I think about it more, it's the break (16.f5) and not the capture (19.fxe6). Good eyes.

 This is similar to an old argument in chess: Reti professed that to put pressure on the center was just as important and perhaps the same as to own the center. As far as I know the argument was never resolved. An certainly, Reti's system of controling the center from the sides remains an important option for most chess players inlcuding those playing at the Master levels.

I am hardly a Master at Chess so I would not argue whether the threat on move 16 is the pawn break or the actual attack at move 19 is the pawn break. Both are important points in the game.