Language question

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This is, perhaps, a stupid question, but hopefully, that means the answer will be simple. I've recently become addicted to Bollywood movies but I want to be able to watch them without subtitles eventually. Thus, I would like to learn the language Bollywood films are in. The problem is that I'm not sure what language that is. I've seen Hindi, Tamil and Urdu listed as the language on DVDs. I am hoping a wiser fan than I can tell me the language I should focus my attention upon. Thanks.