when do u know when its the opening, and the middlegame, and the engame ???

its middle game when all your peices are developed

ah cool

Generally speaking, the middlegame starts when your rooks are connected- so most of your pieces have left the back-rank. There are many definitions of when the endgame begins- it is basically when most of the material has been traded off- a lot of people say after the queens are traded, though that can happen very early, or you may enter a queen endgame!

The middlegame starts when all of your pieces are developed, but there are sometimes exceptions. The endgame starts when most of the material has been traded off.

 can u show me a diagram?

I agree with Nytik, and there was a recent forum topic about this very same thing.  Everyone there seemed to think that it should be an arbitrary number of moves, but connecting the rooks, et. al. seems to be a hallmark of finishing development.  Most of what I've read (The Complete Chessplayer, My System, Bobby Fischer Teaches Chess, Chessmaster, etc.) has backed that idea up.

That thread is here:

http://www.chess.com/forum/view/game-showcase/how-do-we-know-a-game-has-transposed-from-the-opening-to-the-middlegame

The best way to define each stage is to know what you have to do in each stage and when you have to do that you're at the stage.

One thing you will find in chess is that just as important to knowing the 'rules' is knowing the exceptions. No matter what definition you give of 'opening', 'endgame', and 'middle game', you will find there are exceptions to these definitions.

interesting

Middlegame is when you run out of opening theory, so it can come at different times for different players.

So if I'm playing black and my opponent plays 1. c4 or 1. Nf3 I'm in the middle game? I don't think so. I think I'm best off following opening principles at this point. (Yes, I can try to transpose into a theoretical position I know, but this isn't necessarily possible.)