Learn Hardcore Korean: jeoneun naeil sueobeul yeseuphaeyo.

It’s the topic marker. 저는 sets “I/me” as the topic—the thing we’re talking about—rather than strictly marking it as the grammatical subject. It often implies contrast (“as for me…”). If someone asked “Who previews the class?” you’d typically answer with 제가 (subject marker) rather than 저는.

Why use 저는 instead of 나는?

저 is the humble/polite “I,” and it pairs naturally with the polite -요 ending (예습해요). 나 is casual. So:

Polite: 저는 … 예습해요.
Casual: 나는 … 예습해. Mixing 나 with -요 or 저 with casual endings sounds off in standard speech. In texting, you’ll also see the contraction 전 for 저는.

Could I say 제가 내일 수업을 예습해요? What changes?

Yes. 제가 (subject marker) answers or emphasizes “who” does it, often in contrast to others: “I’m the one who previews.” 저는 is more like “as for me,” introducing your own routine or plan without strong contrast.

Why doesn’t 내일 take a particle like -에?

Words like 오늘/내일/어제/지금 usually don’t take -에. You say 내일 by itself. You can add -은/는 for contrast (내일은) or, in rare emphatic/poetic/legal contexts, you might see 내일에, but the default is particleless.

Where can 내일 go in the sentence?

Flexible, but common placements are:

내일 저는 수업을 예습해요. (Fronted time = stronger time emphasis)
저는 내일 수업을 예습해요. (Neutral/natural)
저는 수업을 내일 예습해요. (Focus on “tomorrow” vs some other time) You can also mark contrast: 내일은 수업을 예습해요.

Why is it 수업을, not 수업를?

Because 을/를 follow this rule: after a consonant use 을; after a vowel use 를. 수업 ends in a consonant (ㅂ), so 수업을. Pronunciation links: 수업을 is heard as [수어블] because the final ㅂ links to the following vowel ㅡ.

Is 수업을 예습하다 a natural collocation?

Yes. It means to preview/prepare the content of the class in advance. You’ll also hear:

교과서를/수업 내용을 예습하다 (preview the textbook/the lesson content)
More generally: 수업을 준비하다 (prepare for class; broader than previewing)

What’s the difference among 예습, 복습, 연습, and 준비?

예습: studying material before you learn it in class (preview).
복습: reviewing material after class (review).
연습: practicing skills (drills, exercises).
준비: preparation in a broad sense (materials, planning), not necessarily academic preview.

Why 예습해요 and not 예습을 해요? Are both correct?

Both are correct.

예습해요 treats 예습하다 as a single verb (most common in writing).
예습을 해요 treats 예습 as a noun + 하다 (“do preview”). Slightly more “do the act of previewing,” but in everyday use there’s little difference in meaning.

Does -해요 here mean present or future?

It’s the non-past polite form. With the time word 내일, it naturally refers to a future plan. If you want to make the future explicit:

예습할 거예요 (I’m going to / I will preview)
예습하려고 해요 (I intend to preview)
예습할게요 (I’ll preview, volunteering/assuring)

How would this change in different politeness levels?

Polite: 저는 내일 수업을 예습해요.
Formal polite: 저는 내일 수업을 예습합니다.
Casual: 나는 내일 수업을 예습해.
Plain/written: 나는 내일 수업을 예습한다. Keep 저/나 consistent with the speech level.

Can I drop 저는 or the object particle -을?

Yes, especially in conversation:

내일 수업(을) 예습해요.
내일 예습해요. Korean often omits known subjects and sometimes object particles in speech. For learners, keeping particles helps clarity, especially in writing.

How do I negate this?

Simple negation (don’t): 저는 내일 수업을 예습 안 해요 / … 예습하지 않아요.
Inability (can’t): … 예습 못 해요.
Future refusal: … 예습 안 할 거예요.

How else can I express the same idea?

내일 수업 내용을 미리 공부해요.
내일 배울 내용을 예습해요.
교과서를 미리 읽어요.
수업 준비를 해요 (broader; not limited to academic preview)

How is the whole sentence pronounced naturally?

예습해요 commonly assimilates to [예스패요] (ㅂ + ㅎ → ㅍ).
수업을 links to [수어블].
내일 is [내일] (some speakers merge ㅐ/ㅔ, so it may sound close to [네일]). Altogether you might hear something like: [저는 내일 수어블 예스패요].

Is the spacing correct? 예습해요 or 예습 해요?

Write it together: 예습해요 (noun + 하다 compounds are written as one word). If you use the object-marked version, then: 예습을 해요 (space because 을 is a separate particle).

Can I use 수업에 here?

Not for the object of 예습하다. 수업을 예습하다 = preview the class/content. 수업에 means “in/at class” (a location/time-like use), e.g., 수업에 숙제가 있어요. If you want “for class,” you could say 수업을 위해 예습해요 or 수업에 대비해서 예습해요.