mattaku wakarimasen.

Here, まったく means not at all or absolutely not. It strengthens the negative verb 分かりません.

So:

• 分かりません = I don’t understand
• まったく分かりません = I don’t understand at all

It adds strong emphasis. Depending on tone, it can sound firm: I really don’t understand.

分かりません is the polite negative form of 分かる.

Breakdown:

• dictionary form: 分かる = to understand
• polite stem: 分かり
• polite negative ending: ません

So:

• 分かる = understand
• 分かります = understand / do understand
• 分かりません = do not understand

A plain-form version would be 分からない.

Because 分かる is a godan verb, not an ichidan verb.

Even though it ends in -る, it does not behave like verbs such as 食べる.

Its forms change like this:

• 分かる
• 分からない
• 分かります
• 分かりません

So the る changes to り before ます / ません.

Japanese often leaves out the subject when it is clear from context.

So まったく分かりません could mean:

• I don’t understand at all
• We don’t understand at all
• It’s completely unclear
• I have no idea

The exact English translation depends on the situation. In Japanese, this omission is very normal.

For the same reason: Japanese often omits information that is already understood from context.

For example, this sentence could be short for:

• それがまったく分かりません。 = I don’t understand that at all.
• 日本語がまったく分かりません。 = I don’t understand Japanese at all.
• 何が起きたかまったく分かりません。 = I don’t understand at all what happened.

In natural conversation, leaving that out is very common.

Very often, yes, but not always.

In a sentence like this, まったく works as a strong negative intensifier: not at all.

But まったく can also appear in other ways, for example as an exclamation meaning something like:

• Honestly...
• Good grief...
• Seriously...

So in まったく分かりません, it means not at all, but the word has other uses too.

Not exactly.

• 分かりません = I don’t understand / I can’t tell / it isn’t clear to me
• 知りません = I don’t know

Examples:

• If someone explains grammar and you still don’t get it: 分かりません
• If someone asks a fact and you don’t know it: 知りません

Sometimes English translates both as I don’t know, but the Japanese nuance is different.

Both are correct.

Common ways to write it include:

• 分かりません
• わかりません

Japanese often uses mixed writing like 分かる, where the main meaning is shown with kanji and the grammatical part is written in kana.

In everyday writing, many people also use わかる / わかりません in hiragana, especially because 分かる is such a common word.

So this is mostly a writing choice, not a meaning difference.

It is pronounced roughly like mat-ta-ku.

Important point:

• the small っ means there is a brief pause or doubled consonant before the next sound

So まったく is not mataku. It is closer to:

• mat-ta-ku

That little pause is important in Japanese pronunciation.

Yes. 分かりません is polite because of ません.

However, まったく makes it stronger, so the whole sentence can sound quite firm:

• 分かりません。 = I don’t understand.
• まったく分かりません。 = I don’t understand at all.

It is still polite, but less soft.

If you want to sound gentler, learners often hear things like:

• よく分かりません。 = I don’t really understand.
• ちょっと分かりません。 = I’m not quite sure / I don’t really understand

Yes, they are very similar. Both can mean I don’t understand at all.

A rough comparison:

• 全然分かりません = very common way to say not at all
• まったく分かりません = also not at all, often with a slightly firmer or stronger feel

In many situations, both are natural. The difference is mostly nuance rather than basic meaning.

That space is usually just for learners.

Normal Japanese writing does not usually put spaces between words, so you would normally see:

• まったく分かりません。

Textbooks and study materials sometimes add spaces to make reading easier, but that is not standard everyday writing.