The meaning of 「全然わかる」

Question

I have found several topics on the usage of 「全然」 following a positive term （like this one 全然 {ぜんぜん} with positive adjective / na-adjective)

But I am still confused about the phrase 「全然わかる」

When someone tells me that they think I can understand Japanese:　　

「日本語全然わかる。」

What do they want to imply about my Japanese level when they say this? They think I can understand mostly (like ほとんど), or just roughly (like　だいたい??), or just a little bit?

Thanks!

Answer 1

I think Boaz Yaniv's answer in the question you lined explains the meaning of 全然わかる very well.

The situations I've seen the positive 全然 are all situations where there's an expectation of something "not being X" but it actually "is X". For instance, you'd usually say 全然OKです when someone asks you if something is okay with you and you see that he's not sure whether it is - so you assure him that his negative expectations are completely unfounded and it's completely okay.

全然わかる can be used, for example, after you said you are worried about your Japanese skill:

You: (I think my Japanese is not good...)
Someone: そんなことないよ、（あなたの）日本語全然わかるよ。

... or after someone said you appear not to understand Japanese:

A: あの人は日本語ができないでしょう？
B: いや、日本語全然わかるよ。

In such a situation, 全然 in 全然わかる implies "quite contrary to someone's current (negative) expectation / observation / worry".

Note that 全然 does not imply your current level of Japanese, at least directly. 全然わかる does not necessarily mean your Japanese is perfect. Basically it sounds like "Your/Her Japanese is not bad at all." or "She does understand Japanese."

This type of 全然 is still slangy, so please don't use it in formal settings.

Answer 2

They mean that you can "totally" understand Japanese.
Not in a literal way but... For example, if they ask you if you can understand Japanese, then you say something like "not well" or "just a little", they might reply with something like "全然分かるじゃん！" Which sort of mean "don't be modest! You are totally(very) good!"

Problem is, Japanese people usually get impressed too easily/are too kind and are probably gonna praise you as such for just being able to answer that simple question.