Learn Hardcore Korean: gyuchigeun bandeusi jikyeoya haeyo.

은 is the topic marker. It frames 규칙 (rules) as the topic of the sentence, roughly “as for rules.” It often signals a general statement. Because 규칙 ends with a consonant, the topic marker takes the form 은 (after a vowel it would be 는).

Why is there no subject like “you” or “we”?

Korean frequently drops subjects when they’re understood from context. Here, the sentence states a general rule; the implied subject could be “people,” “we,” or “you.” If you want to state it explicitly, you can say:

우리는/사람들은/여러분은 규칙은 반드시 지켜야 해요. (Pick one subject and keep just one 은/는.)

How strong is 반드시? How does it compare to 꼭?

반드시 means “without fail,” “definitely,” and carries a strong, somewhat formal tone. 꼭 also means “definitely/for sure,” but is more colloquial and slightly softer. In obligation sentences, 반드시 sounds stricter than 꼭.

Is using 반드시 together with -야 하다 redundant?

No—-아/어야 하다 already means “must,” and 반드시 intensifies it to “must, without fail.” Without 반드시, 규칙은 지켜야 해요 still means “you must follow the rules,” just with less emphasis.

What exactly does 지키다 mean here?

지키다 can mean “to keep/observe” rules, promises, etc., and also “to guard/protect.” In this sentence it means “to observe/follow.” Common pairings:

규칙/약속/법을 지키다 = follow rules/keep a promise/obey the law
Antonym: 규칙을 어기다 = break the rules

How does -아/어야 하다 make “must”?

Structure: verb stem + -아/어야 하다.

지키- (stem) + -어야 → 지켜야 (vowel contraction) + 하다 → polite 해요
Present: 지켜야 해요 = must keep
Past necessity: 지켜야 했어요 = had to keep

What’s the difference between 지켜야 해요 and 지켜야 돼요?

Both mean “must/have to.” Nuance:

-아/어야 해요 (하다) feels slightly more normative or prescriptive.
-아/어야 돼요 (되다) can feel more circumstantial or commonly conversational. In everyday speech they’re largely interchangeable. Past forms: 지켜야 했어요 vs 지켜야 됐어요 (both heard; some prefer the matching pair).

Why not say 규칙이 반드시 지켜야 해요?

Because 지키다 is an active verb that takes an object. 규칙이 would be the subject doing the keeping, which doesn’t make sense. If you want the rules as the subject, use the passive:

규칙이 반드시 지켜져야 해요. = The rules must be kept.

Can I use the object marker 을 instead of the topic marker 은?

Yes, with a nuance shift.

규칙은 반드시 지켜야 해요. = As for rules (in general), they must be followed.
규칙을 반드시 지켜야 해요. = You must follow the rules (these rules), focusing more on the object of the action.

What politeness level is 지켜야 해요, and what are common alternatives?

지켜야 해요 is polite informal (요-form), suitable for most day-to-day contexts. Alternatives:

Formal: 지켜야 합니다 (common on signs/announcements)
Casual: 지켜야 해 (friends/peers)
Honorific to the listener: 지키셔야 해요

Where can 반드시 go in the sentence?

Natural placements:

규칙은 반드시 지켜야 해요.
반드시 규칙은 지켜야 해요. (fronted for strong emphasis on “without fail,” stylistic) Avoid splitting the auxiliary: 지켜야 반드시 해요 sounds unnatural.

How is the whole sentence pronounced naturally?

Rough guide: [gyu-chi-geun ban-deu-si ji-kyeo-ya hae-yo]

규칙은 → the final ㄱ links: [규치근]
시 in 반드시 is pronounced like “shi.”
지켜야 is “ji-kyeo-ya.”

Is the spacing correct?

Yes: 규칙은 반드시 지켜야 해요.

Write 지켜야 해요 with a space. Many people type 지켜야해요, but the standard spacing separates the auxiliary 하다.

Do Koreans mark plural for 규칙 here?

No need. 규칙 can mean “rule/rules” from context. 규칙들 is possible but often unnecessary; use it only when you want to stress multiple distinct rules.

Is there a more formal/official way to say this?

Yes, for notices or regulations:

규정을 반드시 준수해야 합니다. Here, 규정 = regulations, 준수하다 = to comply with/observe (formal register).

How do I say “You must not break the rules”?

규칙을 어기면 안 돼요. = You must not break the rules. For extra emphasis: 절대로 규칙을 어기면 안 돼요. Note: Don’t say 지켜야 안 돼요. A negative obligation is typically -면 안 되다.