なぜなら has a more formal nuance.
if I were to arrange them in order from least formal to most formal, I would list them like so:
To be honest, Japanese people don’t really say なぜなら. There is usually a more natural and concise structure that can replace it. Most sentences that would use なぜなら can be rearranged to get rid of it very easily.
Example: 今からご飯を食べます。なぜなら、腹が減ってるからです。(I’m going to eat now because I’m hungry)
Rearranged: 腹が減ってるからご飯を食べます。(because I’m hungry, I’m going to eat now)
Japanese grammar is built to give the reason before the action, as opposed to English, where it’s more natural to state the action and then the reason. English speakers like to carry that over into Japanese by overusing なぜなら, but it’s necessary to adopt the logic of Japanese.
なぜかというとis much more natural in my opinion. It has nuances similar to the English “if I had to say why.”
Please correct me if I’m wrong
While it’s true natives are more likely to use conjunctions for conditionals in normal conversation, you’re mixed up your conjunction in regard to the reasoning.
なぜなら・なぜかというと are objective adverbial condition indicators, so the corresponding conjunction would be ので.
For the OP, I supply the following:
Subjective Adverbial = なので, なぜかといったら
Objective Adverbial = なぜなら (ば), なぜかというと, だから
Subjective Conjunction = から
Objective Conjunction = ので
So, to expand on @YummyFoods answer,
なざなら is your academic, “hard text” usage for objective reasoning. なぜかというと or だから will be your appropriate colloquial terms, depending on the structure, of course. なぜならば is simply more formal than なぜなら.
These are best used if you have to make a long or strong statement that needs space. If you saying something brief, such as @charlesfm example, then you may consider switching to ので if you conditional is objectively causal or から if it is subjectively causal (in which you shouldn’t be using any of the three original constructions anyway ).
Edit: Not saying から is inappropriately placed in your example, of course. More that an objective adverbial like なぜなら is unnatural there unless you want to be matter-of-fact.
Fantastic; you’ve all been very helpful! Thank you.
Thank you for the clarification!!
I wanted to make sure OP knew there are alternatives to the なぜなら structure. I don’t mean to get defensive though; I think you’re 100% right.
I probably (unintentionally?) chose an example where なぜなら sounded out of place to prove my point. Do you happen to have an example of a situation where it would sound completely natural?
By the way, how do you know so much about Japanese grammar?? It’s really impressive.
I know, right?! Reminds me to keep studying…
Matter cannot be created or destroyed because the total mass of matter does not change in a chemical reaction.
Though reading back now, rather than subjective/objective reasoning being the reason its unnatural, its just that it sounds like you’re trying to justify why you’re eating rather than explain why.
Of course, なぜなら + content + から is a natural construction to use when specifically asked a なせ question.
As for my grammar, I translate light novels as a side hobby, so I have a lot of exposure to it. Though, as my grammar is mostly acquired learning from experience, I’m much more likely to be in error than many here who have much more solid studying patterns.