The last thing to know is why it is hard. It's like you're writing a dictionary for a made up language, Elvish, say. It would be a moderate size task to write a dictionary for Elvish with the definitions for your words all in English. What's hard would be writing an Elvish dictionary all in Elvish. If you change the definition of one word that's easy, but then you need to revisit the whole rest of the dictionary to use the new definition idiomatically.