The climax, the most intense part of a story,is the turning point because it determines the outcome of the main conflict. The most important struggle Gurov has is within himself. He easily attracts other womenbut doesn't respect them. When he first meets Anna, he just wants a casual fling. He knows from "really bitter experience" how complicated an affair can be. He keeps this cool attitude toward the affair until he returns home to Moscow. Then he realizes he can't forget about her and goes to her town to find her. It is at this point when he realizes he is no longerthe type of man who can have a casual affair with a woman. Anna has changed him into a responsibleman who no longer feels women are "the inferior race". The two of them truly love each other.

What is the major turning point in Chekhov's "The Lady with the Pet Dog"?

An interesting question. It assumes that the end needs justification, and I'm not sure that is the case. However, if I had to justify the ending in which Gurov distances himself emotionally from the woman, I'd point to subtle points of character in the paragraphs near the end. When the woman exposes her ignorance, it reminds Gurov of his daughter, and this starts a series of thoughts through which he mentally reduces her value to him, and/or judges her. That leads to the final judgment that she is pathetic. So, even if they have/continue an affair, it is painted as sad.

Greg