User blog comment:Meruemgungiplayer/Hatsu/@comment-33963503-20190529125932

It's pretty obvious when you actually speak Japanese. I will not feel weird if somebody ask me "what my Hatsu is?". Hard to explain to you but it's just one of the aspect of Japanese in daily life where you use the verb of the activity to replace its noun form. I believe Chinese and Korean also have that tradition. No people will correct you if you use Hatsu and nen ability interchangeably because we simply know it, although it is actually questionable to use the same logic on a different language. I have no idea whether it works on English or not.

They probably are meaningless to people here, but here are some example sentences in Japanese which use Hatsu to replace nen ability and make perfect sense in conversation:
 * 念獣は「発」の一種. (Nen beast is a certain type of hatsu.)
 * 「発」は自分で決めることができる. (I can determine my hatsu.)

But "hatsu ability" is 100% wrong because it is grammatically incorrect. The word hatsu is a kanji verb which means "release", so "hatsu ability" is something like "release/releasing ability" (発能力) which is very weird to me. You will never ask people "what your releasing ability is?" because the word hatsu is redundant and the meaning of the noun phrase does not make sense. Instead you ask "what your nen ability (念能力) is?" where nen describes what type of ability you are refering to.