Learn Hardcore Japanese: kangosisan ha yasasii hito desu.

It marks 看護師さん (the nurse / nurses) as the topic, i.e., what you are talking about.
The rest of the sentence, 優しい人です, is what you are saying about that topic.

A loose breakdown:

看護師さんは – as for the nurse / nurses…
優しい人です – (they) are a kind person / kind people.

Note that は does not mean is; it simply marks the topic. The copula (the part that works like is / am / are) is です at the end of the sentence.

Why is さん attached to 看護師? Can you just say 看護師?

さん is an honorific suffix that shows politeness and respect.

看護師 = nurse (profession word)
看護師さん = the nurse / that nurse, said politely

Typical usage:

When talking about a nurse (especially one you know, or in a polite situation), 看護師さん is common.
When talking about your own job, you usually do not add さん:
- わたしは看護師です。 – I am a nurse.

So yes, 看護師 by itself is grammatically fine, but 看護師さん is more natural when politely referring to a nurse as a person, not just the job category.

Does 看護師さん mean a nurse, the nurse, or nurses in English?

Japanese has no articles like a / an / the, and nouns usually do not show singular/plural by form.

So 看護師さん can mean:

a nurse
the nurse
nurses (in general)
nurses (a specific group), depending on context

In 看護師さんは優しい人です。, possible interpretations are:

The nurse is a kind person.
Nurses are kind people. (talking about nurses in general)

Which one is correct depends entirely on context, not on the Japanese grammar or word form.

Why do we need both 優しい and 人? Why not just say 看護師さんは優しいです。?

Both are correct, but they have slightly different structure and nuance.

看護師さんは優しい人です。
- Literally: As for the nurse, (they) are a kind person.
- Grammar:
  - 優しい modifies 人: 優しい人 = a kind person
  - 優しい人です = is a kind person
- Feels a bit like describing the nurse’s character / personality.
看護師さんは優しいです。
- Literally: As for the nurse, (they) are kind.
- 優しい works as a predicate adjective (no 人).
- More direct, often used in everyday speech.

In many contexts, English will translate both as The nurse is kind, so the difference is subtle in translation. In Japanese, 優しい人です sounds slightly more like a kind-hearted person, while 優しいです is just (is) kind.

Why is 優しい placed before 人? Can the adjective come after the noun like in English?

In Japanese, adjectives that directly modify a noun always come before the noun.

優しい人 – kind person
大きい家 – big house
新しい車 – new car

You cannot say 人優しい to mean kind person. That would be ungrammatical.

However, when the adjective is the main predicate (i.e., when you are saying X is kind), it comes at the end of the sentence, before です:

この人は優しいです。 – This person is kind.

So:

before a noun: 優しい人
as the predicate: 人は優しいです

What kind of adjective is 優しい, and why isn’t it 優しです?

優しい is an い‑adjective.

Features of い‑adjectives:

Dictionary form ends in 〜い:
優しい, 大きい, 小さい, おもしろい, etc.
In the polite present form, you keep the い and add です:
- 優しいです – is kind
- 大きいです – is big

You do not drop the い before です. So:

✅ 優しいです
❌ 優しです

By contrast, な‑adjectives (like 親切な, 静かな) use です after な / だ forms, e.g.:

親切です (stem 親切, no final い)

What does です do in this sentence?

です is the polite copula, roughly corresponding to is / am / are in English, but it also carries a politeness function.

In 優しい人です:

優しい人 – a kind person
です – makes it (X) is a kind person in a polite way

So:

看護師さんは優しい人です。
≈ (As for) the nurse, (they) are a kind person.

Without です, 優しい人 would just be a noun phrase; です turns it into a complete, polite sentence. In casual speech, です can sometimes be dropped:

看護師さんは優しい人。 (very casual, often in speech)

Could we say 優しい看護師です instead of 優しい人です? What is the difference?

Yes, you can say:

看護師さんは優しい看護師です。

Comparisons:

看護師さんは優しい人です。
- Literally: The nurse is a kind person.
- Focus: their personality / humanity.
看護師さんは優しい看護師です。
- Literally: The nurse is a kind nurse.
- Focus: them as a professional nurse who is kind.
看護師さんは優しいです。
- The nurse is kind. (general, flexible)

All are grammatically correct. The choice depends on whether you want to emphasize them as a person, as a nurse, or just state a quality simply.

Why is は written with the hiragana は but pronounced wa?

This is a quirk of Japanese spelling based on historical pronunciation.

The topic particle is always written with the character は, but pronounced wa.
- 私は学生です。 → read わたし は がくせいです.
In other words:
- As a particle (topic marker), は is pronounced wa.
- As part of a word (e.g., はな, はこ), it is pronounced ha.

So in 看護師さんは優しい人です。, that は is pronounced wa because it is the topic particle.

Do we always need さん after jobs like 看護師?

No, not always. Use of さん after occupations depends on who you are talking about and the social situation.

General guidelines:

About another person, politely:
- 看護師さん – polite and common, especially when talking about a specific nurse.
About yourself:
- わたしは看護師です。 – You do not add さん to your own job.
Generic statements / neutral context:
- Both 看護師は〜 and 看護師さんは〜 can appear; 看護師 sounds a bit more neutral or textbook-like, 看護師さん sounds slightly more people-oriented / respectful.

So さん is polite and often used, but it is not grammatically required; it is about politeness and tone.

Is there a difference between 優しい and 親切な, since both can mean kind?

Yes, there is a nuance difference:

優しい
- Sense: gentle, tender, kind-hearted
- Often about a person’s warmth, softness, emotional kindness.
- Example nuance: someone who speaks gently, is emotionally caring.
親切な
- Sense: helpful, obligingly kind, considerate in action
- Often about doing helpful things for others.
- Example nuance: someone who explains things clearly, helps carry your bags.

In 看護師さんは優しい人です。, the focus is that the nurse is gentle / warm / nice-hearted, not just that they help you. If you want to emphasize that they are helpful, you might say:

看護師さんは親切な人です。 – The nurse is a helpful / considerate person.

Why is there no word for he / she / they in this sentence? How do we know who is kind?

Japanese often omits pronouns like I, you, he, she, they when the subject is clear from context.

In 看護師さんは優しい人です。:

The topic 看護師さん tells us what we are talking about.
There is no need to say She is a kind person; Japanese simply says As for the nurse, (is) a kind person.
The subject (he / she / they) is understood from context (for example, you might be looking at a particular nurse, or talking about nurses in general).

So the sentence is complete and natural in Japanese without a pronoun, even though English almost always needs one.