Learn Hardcore Korean: sueop hue doseogwane gayo. - After class, I go to the library.

수업 means “class,” 후 is the Sino-Korean word for “after,” and -에 turns it into a time adverbial, “after X.” So 수업 후에 literally means “after class.”

Can I say 수업 후 without -에, or use 수업 뒤에 instead?

Dropping -에 (just 수업 후) is understandable in very casual speech or headlines, but in full sentences you normally add -에 for clarity. 수업 뒤에 uses the native Korean word 뒤 (“back, behind”) plus -에, and is also correct; it’s slightly more conversational than 수업 후에.

Why is there an -에 after 도서관 in 도서관에 가요?

With movement verbs like 가다 (“to go”), -에 marks the destination. The pattern is [place] + -에 + 가다/오다 to mean “go/come to [place].”

Could I use 으로 instead of 에 for 도서관으로 가요?

Yes. -으로 can also indicate direction or route (“toward the library”), so 도서관으로 가요 is natural, especially if you want to emphasize the path or means. But for simple “I’m going to the library,” 도서관에 가요 is more common.

What does the verb ending -요 in 가요 signify?

Adding -요 to the verb stem (here 가-) makes the sentence polite and informal (also called the “polite polite” style). It’s the everyday polite ending you use with people you don’t know well or in general polite conversation.

Is 가요 present tense or future?

Korean present tense forms often cover near‐future actions too. So 가요 literally “(I) go,” but contextually it can mean “I will go.” In this sentence, since you say “after class,” it’s understood as “I’ll go to the library after class.”

Why is there no subject (like 저 or 나는) in the sentence?

Korean frequently drops the subject when it’s clear from context. Here the speaker (“I”/저) is implied, so there’s no need to state 저는 or 나는 before the verb.

Can I make this sentence more formal or more casual?

Yes. More formal: 수업 후에 도서관에 갑니다 (using the -ㅂ니다 ending). More casual (among very close friends): 수업 후에 도서관에 가. (dropping polite endings altogether).