Learn Hardcore Japanese: sono toki, kangosisan no yasasii hitokoto de akatyan ga waratte, hahaoya ha totemo uresisou datta. - At that moment, thanks to a kind comment from the nurse, the baby laughed and her mother looked very happy.

Time expressions in Japanese often appear without a particle when they simply set the time of the event, especially at the beginning of a sentence.

そのとき、 看護師さんの優しい一言で…
きのう、 映画を見ました。
(“Yesterday, I watched a movie.”)

You could say そのときに, and it would still be correct, but it adds a slightly stronger sense of “at that specific moment,” or “at that very time.” In everyday narration, そのとき without に is very common and natural.

What does the の in 看護師さんの優しい一言 do?

Here の is a possessive / attributive particle, like English “’s” or “of.”

看護師さんの優しい一言
= “the nurse’s gentle/kind remark/word”

You can think of it as:

看護師さんの一言
“the nurse’s word”
優しい一言
“a kind word”

Combined: 看護師さんの優しい一言
“the nurse’s kind word.”

So 看護師さん is not the subject of the verb here; it’s just showing ownership/association with 一言.

Why is there a さん after 看護師? Does it mean the nurse is female?

さん is an honorific suffix used to show politeness/respect.

看護師 = nurse (neutral, profession name)
看護師さん = “(a/the) nurse” said politely

It does not indicate gender. 看護師さん can refer to a male or female nurse.

In Japanese, it’s common to add さん to many professions or roles when talking about specific people politely:

先生 → 先生 (often without さん because it’s already honorific)
医者 → 医者さん
お医者さん (very common)
店員 → 店員さん

Here, 看護師さん gives a gentle, respectful tone, fitting the emotional, warm context of the sentence.

How do you read 一言, and how is it different from just saying 言葉?

一言 is read ひとこと.

一言（ひとこと） literally “one word,” but more naturally “a (short) remark / a brief comment / a single phrase.”
言葉（ことば） = “word(s) / language / phrase / speech” in a more general sense.

Nuance:

一言だけ言ってくれました。
“He just said a single word / a brief remark.”
優しい言葉をかけてくれました。
“She said some kind words.”

In this sentence, 看護師さんの優しい一言 emphasizes that just one short, gentle phrase from the nurse had a big emotional effect.

What does 一言で mean here? Why is the particle で used?

一言で literally is “by/with one word.”

The particle で here is the means / cause marker:

バスで行きます。 — “I go by bus.” (means/instrument)
その言葉で泣きました。 — “Because of those words, (she) cried.” (cause)

In this sentence:

看護師さんの優しい一言で赤ちゃんが笑って…
“Because of / thanks to the nurse’s gentle word, the baby smiled…”

So 一言で indicates the cause or trigger that made the baby smile.

Why is 赤ちゃん marked with が and 母親 with は?

が and は have different roles:

が marks the grammatical subject, often introducing new or focused information.
は marks the topic: what the rest of the sentence is “about.” It can also imply a contrast.

In this sentence:

赤ちゃんが笑って
“the baby smiled” — 赤ちゃん is the one performing the action; the focus is that the baby smiled (not someone else).
母親はとてもうれしそうだった
“the mother looked very happy” — 母親 is now the topic; we’re shifting attention to how the mother was.

You can feel a slight contrast / shift:

As for the mother, she looked very happy (in reaction to the baby smiling).

What is the function of 笑って in the て-form here? Why not just 笑った?

The て-form of a verb (笑って) is often used to connect clauses, like “and” or “and then,” or to show a cause/result relationship.

赤ちゃんが笑って、母親はとてもうれしそうだった。
Literally: “The baby smiled, and the mother looked very happy.”

If you used 笑った, you would have two separate, more independent clauses:

赤ちゃんが笑った。母親はとてもうれしそうだった。
“The baby smiled. The mother looked very happy.”

Using the て-form makes the actions feel more connected in one flow and can imply a soft cause-effect sequence:

The baby smiled → as a result, the mother looked very happy.

That fits the emotional “because the baby smiled, the mother looked happy” nuance.

Does 笑って modify 母親 at all, or is it only connected to 赤ちゃん?

笑って only belongs to the clause with 赤ちゃん.

Breakdown:

看護師さんの優しい一言で — “because of the nurse’s kind word”
赤ちゃんが笑って、 — “the baby smiled, and…”
母親はとてもうれしそうだった。 — “the mother looked very happy.”

So structurally:

赤ちゃんが笑って — main clause 1
母親はとてもうれしそうだった — main clause 2

The て links the two clauses; it does not turn 笑って into an adjective for 母親. It’s “the baby smiled, and the mother looked very happy,” not “the mother, smiling, looked very happy.”

What’s the difference between 母 and 母親? Why is 母親 used here?

Both relate to “mother,” but they differ in nuance:

母（はは / お母さん）
- はは: “my mother” in humble reference.
- お母さん: “mother / Mom,” used for addressing or referring to someone else’s mother politely or as a title.
母親（ははおや）
- More neutral / formal term: “the mother (as a role/parent).”
- Emphasizes the parental role rather than a personal “Mom.”

In narration or descriptive writing (stories, news, essays), 母親 is very common:

母親は心配そうに赤ちゃんを見ていた。
“The mother was looking at the baby with concern.”

So here, 母親 fits the narrative, third-person storytelling style, focusing on “the mother” as a character/role in the scene.

What does うれしそう mean exactly, and how is it formed?

うれしそう comes from:

うれしい (嬉しい) = “happy, glad”
〜そう (attached to an adjective) = “seems / looks / appears [adjective].”

So:

うれしい → stem うれし
- そう → うれしそう
  = “looks happy,” “seems happy,” “appears happy.”

This pattern works with many i-adjectives:

おいしい → おいしそう — “looks tasty”
悲しい → 悲しそう（かなしそう） — “looks sad”

In the sentence:

とてもうれしそうだった
“(she) looked very happy,”
i.e., from the outside, she appeared to be very happy.

What is the nuance difference between うれしそうだった and うれしかった?

うれしかった
= “was happy” (direct statement of actual internal feeling)
うれしそうだった
= “looked happy / seemed happy” (speaker observes the appearance of happiness)

In narration, you often use 〜そうだ when you’re describing someone from the outside, not directly stating their internal emotions (which you can’t truly know).

So:

母親はとてもうれしかった。
Suggests we’re stating her actual feeling as a fact.
母親はとてもうれしそうだった。
Describes how she appeared: her face, behavior, atmosphere suggested great happiness.

In a third-person scene like this, うれしそうだった feels more natural and “show, don’t tell”–like.

Why is only the last verb だった in the past tense? Is the whole sentence in the past?

Yes, the whole sentence is in the past, even though only the last verb explicitly shows past tense.

Structure:

そのとき、看護師さんの優しい一言で赤ちゃんが笑って、母親はとてもうれしそうだった。

Key point in Japanese:
When multiple actions are linked with the て-form, the final verb’s tense usually applies to the entire sequence, unless something in context says otherwise.

赤ちゃんが笑って、母親はうれしそうだった。
→ both “the baby smiled” and “the mother looked happy” are in the past.

If you needed a different tense for the first clause, you’d express it separately (e.g., with explicit past or future, separate sentences, or additional markers). Here, by ending with だった (past), the sentence clearly describes a completed scene in the past.