kodomo no hannou wo mimasita.

It breaks down like this:

• 子供 = child / children
• の = linking particle, often showing possession or relation
• 反応 = reaction / response
• を = object marker
• 見ました = saw / looked at / observed

So the structure is:

• 子供の反応 = the child’s reaction or the children’s reaction
• 子供の反応を見ました = (I) saw the child’s reaction / (I) observed the children’s reaction

Japanese often leaves out the subject, so I is understood from context.

の connects two nouns.

Here, 子供の反応 means the child’s reaction or more literally reaction of the child.

This particle often works like English ’s or of, but it is broader than that. It can show:

• possession: 田中さんの本 = Tanaka’s book
• relation: 日本の文化 = Japanese culture
• attribute/category: 木の机 = wooden desk

In this sentence, it shows the reaction is related to the child or children.

を marks the direct object of the verb.

The verb is 見ました (saw / observed), and the thing being seen is 子供の反応.

So:

• 子供の反応を = the child’s reaction as the object
• 見ました = saw

Together: saw the child’s reaction

見ました is the past polite form of the verb 見る (to see / to look at / to watch / to observe).

Forms:

• dictionary form: 見る
• polite non-past: 見ます
• polite past: 見ました

So 見ました means saw or sometimes looked at, depending on context.

Japanese very often omits the subject when it is clear from context.

So even though English usually needs I saw..., Japanese can simply say:

• 子供の反応を見ました。

The listener usually understands who did it from the situation, previous sentences, or common sense.

Possible implied subjects could be:

• I saw...
• We saw...
• The teacher saw...

Japanese does not need to state it every time.

It can be either singular or plural.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do. So:

• 子供 can mean child
• 子供 can also mean children

That means 子供の反応 could mean:

• the child’s reaction
• the children’s reaction
• in some contexts, even children’s responses

You decide from context.

Because this sentence is focusing on the object and the action, and the subject/topic is omitted.

Japanese sentences do not always need an explicit は or が. If the speaker and topic are already understood, the sentence can just say what was done:

• 子供の反応を見ました。

If you wanted to include the subject, you could say:

• 私は子供の反応を見ました。 = I saw the child’s reaction.
• 先生が子供の反応を見ました。 = The teacher saw the child’s reaction.

The original sentence is natural because Japanese often leaves that information out.

It can mean several related things depending on context.

見る can mean:

• see
• look at
• watch
• observe

In 子供の反応を見ました, it often feels a little closer to observed the child’s reaction or looked at how the child reacted, especially if someone is paying attention to behavior.

So even if the basic meaning shown is saw, the nuance may be slightly broader.

Here are the common readings:

• 子供 = こども (kodomo)
• の = no
• 反応 = はんのう (hannō)
• を = pronounced o
• 見ました = みました (mimashita)

So the full sentence is pronounced:

こどもの はんのうを みました。
Kodomo no hannō o mimashita.

A note: the particle を is written を but pronounced o in modern Japanese.

Yes. Normal Japanese is usually written without spaces:

子供の反応を見ました。

Learner materials often add spaces to make the structure easier to see:

• 子供　の　反応　を　見ました。

Those spaces are just for learning. In natural writing, you normally would not use them.

Usually, no. The most natural reading is the child’s reaction or the children’s reaction.

That is because AのB most often means B related to A, and here 子供の反応 naturally means the reaction belonging to / shown by the child.

If you wanted to clearly say reaction to the child, Japanese would often use a different structure, such as something involving に対する or another wording depending on the situation.

So in this sentence, learners should understand it as the child’s reaction.

Yes. 見ました is polite Japanese, often called the -ます form in the past tense.

So this sentence is polite but neutral:

• 子供の反応を見ました。

A more casual version would be:

• 子供の反応を見た。

That means the same thing, but it is less polite and more informal.