1. I watched a film on television.

2. I watched a film on the television.

Which one is correct? As somebody told me that the article "the" is not used before the noun "television" but the same is used for "radio" , why so?
Hello Hanuman

My dictionaries say both are correct, but actually "watched it on TV" is much more idiomatic than "watched it on the TV" (in Google, 40,000 hits vs 825 hits). As for the radio, my dictionaries also say that "hear/listen to it on the radio" is more idiomatic than "hear/listen to it on radio". Actually, in Google, "heard it on the radio" hits 169,000 pages whereas "heard it on radio" does only 930 pages. I know you get puzzled at the difference and want to know why they are so, but I feel nobody can give any logical explanation to it. I think they are so just because people speak so.

Yes, I'd say "on television/TV", but "on the radio".

Funny, In English, television is TV , like in Belgium, but here in France, it's Télé...
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I think that we dont use articles when we talk about tv as a form of entertainment. the tv means "a tv set ".

we use articles generally before radio or theather. I guess it is a rule.
 pieanne's reply was promoted to an answer.
Students: We have free audio pronunciation exercises.
Did you see the boat race on (the) television?

Oxford Advanced Learner's Dictionary of Current English, 1974

What's on (the) TV this evening?

There's an interesting play on (the) television.

A Comprehensive Grammar of the English Language, 1985