Learn Hardcore Korean: jigeum hoeuisire sarami ses isseoyo. - There are three people in the meeting room now.

-에 marks a static location or the place where something exists. With 있다/없다 (“to exist/not exist”), use -에: 회의실에 사람이 셋 있어요.
-에서 marks the place where an action happens. Use it with action verbs: 회의실에서 회의해요 (“They have a meeting in the meeting room”).
So for mere existence, -에 is the right choice.

Why is it 사람이 셋 and not 세 명 or 세 사람?

All of these are acceptable, with small differences:

사람이 셋 있어요 feels natural and conversational. It’s a common pattern with people.
세 명 있어요 / 사람이 세 명 있어요 uses the counter 명 (the default counter for people) and is very standard.
세 사람 있어요 is also fine; here 사람 is the noun, not a counter. Pick any of the three; none is wrong in this sentence.

What are the most natural ways to say this sentence?

지금 회의실에 사람이 셋 있어요.
지금 회의실에 세 명 있어요.
지금 회의실에 세 사람이 있어요. All are idiomatic. Choose based on personal preference or the style you’re aiming for.

Do I need the plural marker -들? Why not 사람들이?

No. When a noun is counted or quantified, Korean normally does not add -들. So say 사람이 셋 or 세 명, not 사람들이 셋. Use -들 to emphasize a specific group (“the people as a group”), not for simple counting.

Why use native numbers (셋) instead of Sino-Korean (삼)?

The counter for people (명, and honorific 분) takes native Korean numbers: 한/두/세/네/스무. So say 세 명, not 삼 명. Sino-Korean numbers are used with other counters like 층, 월, 일, 분, 원.

Where can the number go, and why does 셋 sometimes become 세?

Before the noun/counter: 세 사람, 세 명
After the noun with 있다: 사람이 셋 있어요
Native numbers shorten before a noun/counter:
- 하나 → 한, 둘 → 두, 셋 → 세, 넷 → 네, 스물 → 스무

Is 사람 a counter? Do I have to use 명?

사람 is a noun (“person”), not a counter. You can:

Use the counter: 세 명
Use the noun with a number: 세 사람
Use the noun + number after it with 있다: 사람이 셋 있어요 For non-human nouns, you must use the correct counter: e.g., 책이 세 권 있어요 (not 책이 셋 있어요).

Why is it 사람이 (subject marker -이) and not 사람은 (topic -는)?

-이/가 introduces new, factual information (“there are three people”). -은/는 topicalizes or contrasts. 회의실에 사람은 셋 있어요 is possible if you mean “As for people (in contrast to, say, chairs), there are three.” Without contrast, -이/가 is more neutral.

Can I just say 셋 있어요?

Yes, if the context already makes it clear you are talking about people (e.g., someone asked “How many people are there?”). Otherwise include the noun: 사람이 셋 있어요 or 세 명 있어요.

How do I make this honorific for respected people?

Use the honorific counter 분 and the honorific verb 계세요 (honorific of 있어요 for people):

지금 회의실에 세 분 계세요. Formal style: 세 분 계십니다.

What politeness level is 있어요, and what are the alternatives?

있어요: polite informal (해요체)
More formal: 있습니다
Casual: 있어
Negative: 없어요 / 없습니다

Can I move 지금 or change the order?

Yes. Typical neutral order is time → place → subject → rest → verb:

지금 회의실에 사람이 셋 있어요. You can also say:
회의실에 지금 사람이 셋 있어요. (acceptable)
With contrast: 지금은 회의실에 사람이 셋 있어요. (emphasizes “as for now”)
회의실에는 사람이 셋 있어요. (emphasizes/contrasts the location)

What’s the difference between 지금 and 이제 here?

지금 = “now” as a point in time (neutral).
이제 = “now (from this point onward)” and often implies a change of state. In this sentence, 지금 is the natural choice. 이제 회의실에 사람이 셋 있어요 can sound like “As of now (not before), there are three.”

Pronunciation tips for this sentence?

회의실 is commonly pronounced close to [회이실]; many also say [회의실]. The 의 after a vowel often sounds like 이.
사람이 is [사라미].
Across the boundary, 셋 있어요 links as [세시써요] (the final ㅅ of 셋 moves to the next syllable before the vowel in 있어요).

Can I say 회의실 안에 instead of 회의실에?

Yes. 회의실 안에 explicitly means “inside the meeting room,” which is fine here. 회의실에 already implies “in/at the meeting room,” so both are natural.

How do I say there are zero people?

지금 회의실에 사람이 없어요.
Stronger: 지금 회의실에 한 사람도 없어요. (“not even one person”)

How do I ask the matching question?

Neutral: 지금 회의실에 몇 명 있어요?
Also fine: 지금 회의실에 몇 사람 있어요?
Honorific: 지금 회의실에 몇 분 계세요?