This dialogue is from the 2000 film 'Kaho Naa... Pyaar Hai' starring Hrithik Roshan. The line 'Iska matlab, woh iss shakk ko pehchanante hai' reflects the romantic mystery element of the story. 'Baazi', 'Dil', and 'Baazigar' are other Bollywood titles but not the source of this dialogue.