zyouro ni mizu wo ireru.

じょうろ means watering can.

It is often written in hiragana because its kanji form, 如雨露, is rare and not very useful for most learners. In everyday Japanese, you will usually see じょうろ, not the kanji.

Here, に marks the destination or target location of the action.

In じょうろ に 水 を 入れる, the water is being put into the watering can, so じょうろ に means into the watering can.

A useful pattern is:

place/container に thing を 入れる
= put thing into place/container

を marks the direct object of the verb.

The verb 入れる means to put in / insert, so the thing being put in is the direct object. In this sentence, that thing is 水.

So:

• 水 を = water as the thing being put in

Japanese normally follows SOV word order: subject - object - verb.

English says:

put water into the watering can

Japanese puts the verb last:

じょうろ に 水 を 入れる

This is very normal in Japanese. The verb usually comes at the end of the sentence or clause.

The structure is:

container に thing を 入れる

In this sentence:

• じょうろ に = into the watering can
• 水 を = water
• 入れる = put in

So the grammar is showing:

Put water into the watering can.

No subject is stated explicitly.

Japanese often leaves out the subject when it is obvious from context. Depending on the situation, this sentence could mean:

• I put water into the watering can
• You put water into the watering can
• Put water into the watering can
• Someone puts water into the watering can

Without context, it is just the basic action: put water into the watering can.

入れる is transitive, because it takes a direct object marked by を.

Here, 水 is the object:

• 水 を 入れる = put in water

Its intransitive partner is 入る, which means to enter / to go in / to be contained.

Compare:

• 水 を 入れる = put water in
• 水 が 入る = water goes in / water is contained

This pair is very common and worth memorizing:

• 入れる = to put in
• 入る = to go in

This is normal Japanese writing.

Some words are commonly written in kanji, while others are usually written in hiragana. 水 is a very common basic kanji, so it is normally written that way. じょうろ, on the other hand, is usually written in hiragana because its kanji form is uncommon.

So this mixed writing style is completely natural.

In most cases, に is the natural choice with 入れる.

へ mainly emphasizes direction toward something, while に works better for the endpoint or container of an action. Since a watering can is the container that receives the water, に is the standard particle here.

So:

• じょうろ に 水 を 入れる = natural
• じょうろ へ 水 を 入れる = possible in some contexts, but less standard here

You are right: normal Japanese writing usually does not use spaces.

This sentence would normally be written as:

じょうろに水を入れる。

Spaces are often added in textbooks or beginner materials to make the grammar easier to see.

The polite form is 入れます.

So the sentence becomes:

じょうろに水を入れます。

This is more appropriate in polite speech or neutral formal situations.

Yes, Japanese word order is somewhat flexible, as long as the particles make the roles clear.

For example, these are both understandable:

• じょうろに水を入れる
• 水をじょうろに入れる

Both mean essentially the same thing.

However, the most natural order depends on context and emphasis. The original sentence is very straightforward and natural.

By itself, 入れる is the plain dictionary form, so the exact nuance depends on context.

It can be used for:

• a general action: to put water into the watering can
• a habitual action: (someone) puts water into the watering can
• instructions in manuals/recipes: put water into the watering can

If you wanted a clear command, Japanese would often use a command form such as 入れて or 入れなさい, depending on tone and situation.

入れる is pronounced いれる.

Even though the kanji is 入, the full verb has its own reading in this word. Japanese verbs often combine kanji with okurigana, the hiragana that follows the kanji.

So:

• 入 = kanji root
• れる = hiragana ending
• 入れる = いれる

This is very common in Japanese verbs.