how to tell if a move is blunder in analiisis?

????

Look at the evaluation score graph. Anyplace you see a large jump, that's a blunder or mistake, and when it shifts from + to - or vice-versa, it's a losing blunder.

The difference between "blunder" and "mistake" is an arbitrary point in terms of centipawn loss. (The size of the jump is centipawn loss for that move.) The scale of the graph is approximately logarithmic, meaning that the jump on the graph will appear smaller when one side already has a significant advantage.

oh i got it thanks

Ah but a blunder is only a blunder if the opponent uses the advantage and wins. It should be called a mistake if the person still wins after making the not good or ideal move. This is one opinion.

@Rarelyadraw Nah, if the opponent does not find it, it's just a counter-blunder. This is what is meant by "luck" in Chess Insights... when you blunder and your opponent misses the best continuation. (Conversely, "opportunism" is when your opponent blunders and you DO find it.)

At the end of a match of chess one can look for the “game ending move/ blunder” vs just a “oops got away with it blunder/mistake”? Just another different example of how “blunder” can and is used.