how to convert english word to marathi

The solution is impossible (at least for beginners!).

Why?

You first need to know that there is no mechanism that can convert the data from one understandable language to another one. You need to do a lot of underground stuff, to read the words and then convert them to their translated nodes. Whereas, an offline application (if created) would be more like a 1 GB application, having all of the dictionary stuff and other required grammar and sentence structure base.

Using Google or Bing APIs is the best (possible) solution to this problem. Offline requires a lot of stuff. Which is not possible! At least in this forum, article would be a good thing.