kono hako ga saidai desu.

It is pronounced:

kono hako ga saidai desu

A more detailed breakdown:

• この = kono
• 箱 = hako
• が = ga
• 最大 = saidai
• です = desu

A natural spoken pronunciation may sound a little like:

kono hako ga saidai des

because u in desu is often very weak or almost silent.

この must be followed by a noun, while これ stands by itself.

• この箱 = this box
• これ = this one / this

So:

• この箱が最大です。 = This box is the largest.
• これが最大です。 = This one is the largest.

You cannot normally say これ箱.

In Japanese, demonstratives like この go before the noun they describe.

So:

• この箱 = this box
• その箱 = that box
• あの箱 = that box over there

This is similar to English word order, where this also comes before box.

が marks the subject of the sentence.

In この箱が最大です。, が tells you that this box is the thing being identified as largest / maximum.

A very simple way to think of it here is:

• この箱が = as for which thing is the largest? this box
• 最大です = is the largest

So が helps focus on this box as the item being singled out.

This is a very common question. Both can be possible, but the nuance changes.

• この箱が最大です。
  This emphasizes that this box is the one that is the largest.
• この箱は最大です。
  This presents this box as the topic and says that, regarding it, it is the largest.

In many cases:

• が is used when identifying or highlighting the specific item
• は is used when talking about something as the topic

If you are comparing several boxes and pointing out which one is the largest, が feels very natural.

最大 literally means maximum or largest.

It is often used in contexts involving comparison, size, amount, scale, or degree. In this sentence, it means that this box is the biggest one in the relevant group.

A few related examples:

• 最大の箱 = the largest box
• 最大サイズ = largest size
• 最大の問題 = the biggest problem

Compared with 一番大きい, 最大 can sound a bit more formal, technical, or objective.

They mean different things.

• 大きい = big
• 一番大きい = the biggest
• 最大 = largest / maximum

So:

• この箱は大きいです。 = This box is big.
• この箱が一番大きいです。 = This box is the biggest.
• この箱が最大です。 = This box is the largest.

最大 is often used when comparing within a set and can sound more formal than 一番大きい.

It does not behave exactly like a regular -i adjective such as 大きい.

You can think of 最大 as a word meaning maximum/largest that can function as a predicate with です:

• この箱が最大です。

It can also modify a noun with の:

• 最大の箱 = the largest box

So it does not act like an -i adjective. You would not say 最大い.

Because この directly modifies the noun by itself. It does not need の.

Correct:

• この箱 = this box

Not correct:

• このの箱
• この箱の as a way to mean this box by itself

The word の is used in other structures, but not between この and the noun it modifies.

Not exactly.

In beginner translations, です is often matched with is / am / are, and that is useful for understanding. But grammatically, です is not exactly the same kind of word as English is.

In this sentence, です makes the statement polite:

• この箱が最大です。 = polite
• この箱が最大だ。 = plain

So です is better thought of as a polite sentence ending or polite copula rather than a perfect one-to-one equivalent of English is.

No. Japanese does not have articles like a and the.

So この箱が最大です。 does not contain a separate word meaning the. The idea of the largest comes from context and from the meaning of 最大.

This is very common in Japanese. Whether something is a box, the box, or just box often depends on context rather than a separate article.

Yes, it is grammatical and natural, especially in a context where several boxes are being compared.

However, the nuance matters:

• この箱が最大です。 sounds a bit formal or objective
• この箱が一番大きいです。 may sound more everyday and conversational

So if you are speaking casually in daily life, many people might choose 一番大きい. But 最大 is absolutely normal, especially in more formal, written, technical, or comparison-focused contexts.

Yes. Japanese often leaves that understood from context.

For example, if several boxes are on a table, someone can say:

この箱が最大です。

and everyone understands that it means this box is the largest among these boxes.

The comparison group does not need to be stated if it is already clear from the situation.