Learn Hardcore Korean: daebubun saramdeureun yeonhyue swieo.

쉬어 is informal intimate (banmal). Use it with close friends, younger people, or in inner monologue.
Neutral polite: 쉬어요 → 대부분 사람들은 연휴에 쉬어요.
Formal polite: 쉽니다 → 대부분 사람들은 연휴에 쉽니다.
Plain/written style: 쉰다 → 대부분 사람들은 연휴에 쉰다.

Why is it 사람들은 with 은, not 는?

The topic marker alternates:

After a consonant: 은
After a vowel: 는 Since 사람들 ends in the consonant ㄹ, you add 은 → 사람들은.

Do I need the plural marker 들 in 사람들 here?

No. Korean plural 들 is optional and often omitted when plurality is obvious.

Very natural: 대부분(의) 사람들은 …
Also possible (more compact): 대부분은 연휴에 쉬어. (“Most [of them] rest during the holidays.”) Using singular with “most,” like 대부분(의) 사람은, is less common; prefer 사람들 or switch to 대부분은.

Should it be 대부분 사람들 or 대부분의 사람들?

Both are correct:

대부분 사람들: colloquial, frequently heard in speech.
대부분의 사람들: a bit more careful/standard. Meaning and nuance are essentially the same; choose based on formality.

Why is the topic marker on people (사람들은) instead of the time word (연휴에)?

Using 은/는 on 사람들 frames a generalization about people: “As for most people, (they) rest…” You could put the topic on the time to spotlight the time frame:

연휴에는 대부분 사람들(이) 쉬어. (As for holidays, most people rest.)

Could I use the subject marker 이/가 instead of 은/는?

Yes:

대부분의 사람들이 연휴에 쉬어. This feels a bit more informational/neutral (who is it that rests? → “most people do”). With 은/는, you sound more like you’re making a broad, topic-level generalization.

Why is it 연휴에 and not 연휴에서?

-에 marks time (“on/at/during” a time point/period) → 연휴에 is correct.
-에서 marks a place where an action happens; it’s not used for time. 연휴에서 would be ungrammatical here.

What’s the difference among 연휴에, 연휴 동안, 연휴 때, and 연휴에는?

연휴에: “during the holiday period” (neutral, default time marker).
연휴 동안: emphasizes duration (“for the whole holiday”).
연휴 때: casual “at/during the time of the holiday.”
연휴에는 (or contracted 연휴엔): uses the topic marker to contrast/highlight holidays.

Is 연휴 the same as “holiday”? How is it different from 휴일, 공휴일, or 명절?

연휴: a stretch of consecutive days off (e.g., a long weekend).
휴일: a day off (any non-working day).
공휴일: an official public/national holiday.
명절: a traditional holiday/festival (e.g., 설날, 추석).

Is the word order fixed? Can I move things around?

Korean word order is flexible before the verb. These are all natural:

대부분 사람들은 연휴에 쉬어.
연휴에는 대부분 사람들은 쉬어.
대부분 사람들은 쉬어, 연휴에. (afterthought/colloquial) Keep the verb at the end; rearranging mainly changes emphasis.

How is 쉬어 pronounced, and how is it different from 쉬워?

쉬어 [쉬어] = from 쉬다 (“to rest”).
쉬워 [쉬워] = from 쉽다 (“to be easy”). They look similar but are different verbs and vowels. Don’t say 쉬워 when you mean “rest.”

Could I say this without mentioning “people,” like “Most of them rest during the holidays”?

Yes, use 대부분 as a pronoun with a particle:

대부분은 연휴에 쉬어. (Most [of them] rest during the holidays.)
With subject marker: 대부분이 연휴에 쉬어. (Often needs context clarifying who “most” refers to.)

Can particles be dropped in casual speech here?

They often are in fast, casual speech, but it’s safer to keep them while learning:

Full: 대부분 사람들은 연휴에 쉬어.
Dropped (very colloquial): 대부분 사람들 연휴에 쉬어. Write and practice with particles to avoid ambiguity.

Any other natural ways to say “most people” here?

대다수(의) 사람들은 연휴에 쉬어. (slightly more formal/weighty)
사람들은 대부분 연휴에 쉬어. (placing 대부분 adverbially)
대부분은 연휴에 쉬어. (pronoun-like “most [of them]”)

If I want a very formal written style, which verb ending should I use?

Use the formal declarative:

대부분 사람들은 연휴에 쉽니다. In neutral written prose (e.g., headlines or general statements), the plain style is also common:
대부분 사람들은 연휴에 쉰다.