Learn Hardcore Korean: sae gyujeongi naeilbuteo jeogyongdwaeyo. - The new regulations apply starting tomorrow.

Korean often uses the polite present (-아요/어요) for near‑future, scheduled, or arranged events, especially when a time expression like 내일부터 (from tomorrow) makes the timing clear. It’s natural and common.

More explicitly future: 적용될 거예요 or the formal 적용될 것입니다.
Announcement style: 적용됩니다 (formal present, also used for scheduled future).

What does the particle 이 in 규정이 do, and why not 가?

이/가 is the subject marker. Use 이 after a noun ending in a consonant and 가 after a vowel. 규정 ends with a consonant, so 규정이 is correct. If the noun ended in a vowel, you’d use 가.

Can I use 은/는 instead of 이/가? What’s the nuance?

Yes: 새 규정은 내일부터 적용돼요.

이/가 introduces or focuses the subject as a fact.
은/는 marks a topic and often implies contrast or a shift of topic. With 규정은, you might be contrasting the new rules with other rules or with what happened before.

Why 새 규정 and not 새로운 규정? Are both correct?

Both are correct.

새 규정: the most natural, neutral choice in everyday speech and writing.
새로운 규정: slightly more descriptive or emphatic on “newness,” and a bit heavier in tone. In many contexts they are interchangeable.

What’s the difference between 적용되다 and 적용하다?

적용되다: passive, “to be applied.” Your sentence: 새 규정이 … 적용돼요 = “The new regulations are applied.”
적용하다: active, “to apply (something).” Active version: (우리가/회사가) 내일부터 새 규정을 적용해요.

Is the spelling 돼요 correct? I’ve seen 되요 too.

Spell 돼요. Here’s why:

되다 + 어요 → 되어요 → 돼요 (contracted form).
되요 is a very common mistake and is considered incorrect in standard spelling.
Formal non‑contracted style appears in writing as 되어요, but in speech 돼요 is overwhelmingly used.

How do I pronounce the sentence naturally?

새 [sæ]
규정이 [gyu-jeong-i] (no n‑sound; the ㅇ just carries the vowel)
내일부터 [nae-il-bu-teo]
적용돼요 approximately [jeo-gyong-dwae-yo]. In fast speech, 적용 sounds like [저굥], and 돼요 like [돼요]/[되요] in sound but spelled 돼요.

Can I move 내일부터 to the front?

Yes. Word order is flexible for adverbials.

내일부터 새 규정이 적용돼요. (very natural)
새 규정이 내일부터 적용돼요. (also natural) Fronting 내일부터 emphasizes the start time.

What level of politeness is 적용돼요? How would I make it more formal or more casual?

적용돼요: polite informal (해요체), good for most conversations.
More formal/announcement: 적용됩니다.
Casual/plain: 적용돼 (no 요).
Very formal future: 적용될 것입니다.

Does 규정 mean one regulation or multiple regulations? Do I need 들?

Korean often leaves number unspecified. 새 규정 can mean “a new regulation” or “new regulations,” depending on context. You can add 들 (e.g., 새 규정들) to stress plurality, but it’s usually unnecessary with words like 규정.

Is 적용되다 the best verb for rules starting to take effect? What about 시행되다 or 발효되다?

시행되다: “to be enforced/come into effect,” very common for rules and policies. Example: 새 규정이 내일부터 시행돼요.
적용되다: “to be applied (in practice),” often about how rules are used in cases or to people.
발효되다: “to come into force” (often for treaties/laws). Less common for internal company rules but possible in legal/formal contexts.

Why use 부터 after 내일? Could I use 에 instead?

부터 marks the starting point: 내일부터 = “starting from tomorrow.”
내일에 적용돼요 sounds like “applies on tomorrow” and is not the natural way to express a start point. Use 내일부터.
If you need an end point: 내일부터 다음 달까지 적용돼요.

Is there a space between 내일 and 부터?

No. Particles attach to the preceding noun with no space: 내일부터 (not “내일 부터”).

How do I make this a question, like “Will the new regulations apply from tomorrow?”

Just use rising intonation or add a question mark:

새 규정이 내일부터 적용돼요? For a more explicit future: 새 규정이 내일부터 적용될 거예요? Formal: 새 규정이 내일부터 적용됩니까?

How do I mention who is applying the rules?

Use the active form with 적용하다:

회사가 내일부터 새 규정을 적용해요. (The company will apply the new regulations from tomorrow.) In a passive sentence, the agent can be added with 에 의해, but it’s formal/literary:
새 규정이 내일부터 회사에 의해 적용돼요.

Can I say 적용이 돼요 instead of 적용돼요?

They’re related but not the same structure.

적용돼요 = the verb 적용되다 (be applied).
적용이 돼요 = the noun 적용
- 이
  - 되다 (“application happens”). It’s idiomatic in some contexts (e.g., 할인 적용이 돼요), but with your subject (새 규정이) the verb 적용되다 is the natural choice.