User blog comment:AtlasFlame206/Is there gonna be a possible Fairy Tail/Rave Master crossover story arc?/@comment-99.234.126.128-20130822054644/@comment-7418318-20130824112350

There are also little things like the different "politeness levels" in the japanese language that are hard to translate, along with the name-suffixes and gender neutral pronouns.

Quite often you'll see "X-sama" unilaterally translated as "Lord X" for example which can be correct, but often "honored X" is more appropriate.

There's also the different length of words to consider. The english dub can't just make the correct translation, they also have to match the english words to the lip movement of the characters. While in anime this is easier than with real actors, it's still not a trivial task.