Learn Hardcore Korean: wonrae sueobeun ojeon 10sie sijakhaeyo.

It means “originally/by default/usually,” signaling the normal rule or schedule. It can subtly set up a contrast, as in “Normally it starts at 10, but (not today).” It doesn’t have to imply a change, but it often invites that interpretation in context.

Can I say 원래는 instead of 원래? What’s the difference?

Yes. 원래는 adds a topic marker, making the contrastive nuance stronger: “As for normally/Originally, …”

원래 수업은 … = natural, slightly contrastive because of 원래 itself.
원래는 수업이 … = clearly topicalizes “originally,” inviting contrast.
Avoid stacking heavy topics like 원래는 수업은 … unless you really want a double-topic feel.

Why is 수업 marked with 은 (topic) instead of 이 (subject)?

수업은 sets “the class” as the topic (“as for the class”), which is very common in conversational Korean, especially when comparing or giving general facts. 수업이 would mark it as the grammatical subject without the same “as for” or contrastive nuance.

Is “수업이 오전 10시에 시작해요” also correct?

Yes. 수업이 … 시작해요 is perfectly grammatical and neutral. 수업은 … 시작해요 sounds a bit more like you’re presenting a known topic or contrasting with something else (e.g., “The class starts at 10; the meeting starts at 11”).

What’s the difference between “수업이 시작해요” and “수업을 시작해요”?

수업이 시작해요 = “The class starts” (intransitive; the class is the subject).
수업을 시작해요 = “(We/I) start the class” (transitive; an implied agent starts it).
Both are common but express different perspectives (event vs. someone doing it).

How is 시작되다 different from 시작하다?

시작하다 = “to start/begin (something)” or “(something) starts” (often intransitive too).
시작되다 = passive: “to be started/begun,” “to get underway.”
For schedules, both 수업이 시작해요 and 수업이 시작돼요 are heard; 시작해요 is a bit more neutral; 시작돼요 can sound slightly more formal or report-like.

Why is the ending 해요 used? Can I use 합니다 or 해?

시작해요 = polite, neutral (most common in everyday speech).
시작합니다 = formal polite (announcements, news, presentations).
시작해 = casual (with close friends or younger people). Choose based on the level of politeness/formality you need.

Does the present tense here mean “is starting now” or “starts (as a rule)”?

Here it states a general fact/schedule: “(normally) starts at 10 a.m.” Korean present tense often covers habitual or scheduled actions, not just “right now.”

Can I say “시작하고 있어요” for “is starting”?

Generally no. 시작하다 is instantaneous, so the progressive sounds awkward. Use:

지금 시작해요 (We’re starting now.)
막 시작했어요 (It just started.)

Why is 에 used after 10시? Can I drop it or use 부터?

에 marks a point in time (“at 10 o’clock”).
In casual speech, 에 can be dropped: 오전 10시 시작해요 (still natural).
부터 means “from,” so 10시부터 시작해요 is also natural (“It starts from 10”), with almost the same meaning in this context.

Which number system is used with 시? How do I read 오전 10시?

Hours with 시 use native Korean numbers. So 10시 is read 열 시 (not “십 시”). Minutes use Sino-Korean numbers. Examples:

10:00 = 열 시
10:30 = 열 시 반 or 열 시 삼십 분
10:15 = 열 시 십오 분

How is the sentence actually pronounced in connected speech?

Common pronunciations:

원래 → [월래]
수업은 → [수어븐] (the ㅂ links to the vowel of 은)
오전 → [오전]
열 시에 (10시에) → often [열씨에] due to tensification
시작해요 → often [시자캐요] (ㅎ assimilation) Full flow: roughly [월래 수어븐 오전 열씨에 시자캐요].

Can I move 원래 around? What word orders are natural?

Yes. All of these are natural, with slight emphasis shifts:

원래 수업은 오전 10시에 시작해요.
수업은 원래 오전 10시에 시작해요. (very common)
수업은 오전 10시에 원래 시작해요. (okay, but less common) Putting 원래 early tends to highlight the “normally/by default” idea for the whole sentence.

Is 오전 necessary? Could I use 아침 instead?

오전 10시 is the standard way to say “10 a.m.” in schedules.
아침 10시 is colloquial and understandable but less standard/formal.
You can omit 오전/오후 if context makes it clear, but then 10시 is ambiguous between AM/PM.

Are the spacing and attachments in “오전 10시에” correct?

Yes:

Space between 오전 and 10시: 오전 10시
No space between the numeral and counter: 10시
The particle attaches without a space: 10시에 If you spell out the hour: 열 시에 (space between native number and counter).

Could I drop 수업 if context is clear?

Yes. In context, 원래 (오전) 10시에 시작해요 would be understood as “It normally starts at 10,” with the subject (the class) omitted as a known topic.

How do I ask “What time does the class start?”

Use:

수업은 몇 시에 시작해요? (polite, with topic nuance)
수업이 몇 시에 시작해요? (polite, neutral)