赤ちゃん

赤ちゃん

Baby.

In this sentence, '赤ちゃん' refers to a baby as the subject performing the action of laughing.

赤ちゃんが笑った。

The baby laughed.

Here, '赤ちゃん' is the indirect object, indicating the receiver of the milk.

彼女は赤ちゃんにミルクをあげている。

She is giving milk to the baby.

In this context, '赤ちゃん' is the noun modified by the clause indicating the baby that is playing in the park.

公園で遊んでいる赤ちゃんを見た。

I saw a baby playing in the park.