Learn Hardcore Korean: pigonhanikka jibeseo swieoyo. - Because I’m tired, I rest at home.

It’s a connective meaning because/since. It links a reason clause to a result clause. In 피곤하니까 집에서 쉬어요, the reason is 피곤하니까 (because [someone is] tired) and the result is 집에서 쉬어요 (rest at home). The reason typically comes first in Korean.

Why is it 피곤하니까 and not 피곤해니까?

With -(으)니까, you attach it to the verb/adjective stem. The stem of 피곤하다 is 하-, so it becomes 피곤하니까.
The form 해 is the contraction of 하여 used with endings like -요 (e.g., 피곤해요), but you don’t use 해 before -니까. Similarly:

좋다 → 좋으니까
바쁘다 → 바쁘니까
필요하다 → 필요하니까

What’s the difference between -(으)니까 and -아서/어서 in this sentence?

Both can mean “because,” but:

-(으)니까 often presents a reason as the speaker’s judgment/justification and is the natural choice when the main clause is a command or suggestion.
-아서/어서 often expresses a natural cause/effect or background reason and, in careful standard Korean, is generally avoided when the main clause is an imperative/propositive.

Compare:

피곤하니까 집에서 쉬어요. (can sound like a suggestion: “Since we’re tired, let’s rest at home.”)
피곤해서 집에서 쉬어요. (more like stating a reason for a fact/habit: “I rest at home because I’m tired.”)
For making a suggestion/request, -(으)니까 is preferred.

Is this a statement, a suggestion, or a request?

By form, 쉬어요 (polite present) can be:

A statement: “(I) rest at home.”
A polite suggestion when the subject is “we”: “Let’s rest at home.”

It is not a proper request to “you.” For a request, use 쉬세요. Context (and often adding 우리) disambiguates:

피곤하니까 우리 집에서 쉬어요. → “Since we’re tired, let’s rest at home.”

How would I say “Please rest at home (since you’re tired)”?

Use the polite imperative -세요:

피곤하시니까 집에서 쉬세요. (honorific “you,” respectful)
Without honorific: 피곤하니까 집에서 쉬세요.

Why is it 집에서 and not 집에?

-에서 marks the place where an action occurs (at/in). 쉬다 is an action, so 집에서 쉬다 = “rest at home.”
-에 marks destination or static location (to/at). You’d use 집에 with verbs like 가다 (go) or 있다 (be):
- 집에 가요 = “I’m going home.”
- 집에 있어요 = “I’m at home.”
  Saying 집에 쉬어요 is unnatural.

Do I need to say “I” or “we” explicitly?

No. Korean often drops subjects when clear from context. You can add them for clarity:

저는 피곤하니까 집에서 쉬어요. (I’m tired, so I rest at home.)
우리 피곤하니까 집에서 쉬어요. (We’re tired, so let’s rest at home.)

What is the dictionary form of 쉬어요, and how is it conjugated?

Dictionary form: 쉬다 (to rest).
Conjugation to polite present: 쉬다 → 쉬어(요) → 쉬어요.
Pronunciation is typically [쉬어요] or [쉬여요]. It’s not from 시다, so don’t confuse it with 셔요 (which comes from verbs like 마시다 → 마셔요).

What’s the difference between 쉬어요 and 쉬세요?

쉬어요: polite present. Statement about resting, or a soft suggestion if the implied subject is “we.”
쉬세요: polite imperative with honorific; a request telling someone respectfully to rest.
Examples:
피곤하니까 집에서 쉬세요. (Please rest at home since you’re tired.)
피곤하니까 집에서 쉬어요. (Since we’re tired, let’s rest at home / I rest at home.)

Can I say 피곤해서 집에서 쉬어요 instead?

Yes, it’s grammatical and natural as a statement of reason. Nuance:

피곤해서… sounds like a straightforward cause (“because I’m tired, I (tend to) rest at home”).
피곤하니까… can feel more like the speaker’s justification or a lead-in to a suggestion/command.
For explicit suggestions/requests, -(으)니까 is the safer, more standard choice.

Can the reason clause come second, like “I’ll rest at home because I’m tired”?

Yes. You can say:

집에서 쉬어요, 피곤하니까.
This is common in speech as an afterthought. Both orders are fine.

How can I change the tense or nuance?

Future/intention: 피곤하니까 집에서 쉴 거예요. (I’ll rest at home because I’m tired.)
Immediate intention (responsive): 피곤하니까 집에서 쉴게요.
Past: 피곤했으니까 집에서 쉬었어요.
Clear suggestion: 피곤하니까 집에서 쉬자 (plain) / 쉬어요 (polite “let’s”).

Does the honorific need to appear in the reason clause too?

If the subject of “being tired” is an honorific subject (e.g., the listener), use honorific marking there:

(선생님이) 피곤하시니까 집에서 쉬세요.
If the subject is “I,” don’t use honorific:
(저는) 피곤하니까 집에서 쉴게요.

Any common mistakes to avoid with this sentence?

Spelling: write 피곤하니까, not 피곤하니깐.
Don’t use 집에 with 쉬다; use 집에서.
For a request to “you,” don’t use 쉬어요; use 쉬세요.
Don’t try 피곤해니까; it must be 피곤하니까.

Is there any subtle nuance difference between -(으)니까 and -아서/어서 beyond imperatives?

A rule of thumb:

-아서/어서 often describes objective, natural cause-and-effect or background circumstances.
-(으)니까 often presents the speaker’s reasoning or justification, frequently leading to a suggestion, decision, or command.
In everyday conversation the two overlap a lot, but this guideline helps choose the more natural connector for your intent.