Learn Hardcore Korean: beoseureul tamyeon doni jeoryakdwaeyo.

-면 is the conditional suffix meaning “if/when.” You attach it to the verb stem (타 + 면 → 타면) to say “if/when (you) ride.” Because 타 ends in a vowel, you use -면 rather than -으면.

Why is 버스 marked with -를 in 버스를 타면?

In Korean, 타다 (“to ride”) is a transitive verb, so the thing you ride takes the object particle -를/을. Since 버스 ends in a vowel, it becomes 버스를 타다 (“to take the bus”).

Why is 돈 marked with -이 in 돈이 절약돼요 instead of 돈을?

Here 절약되다 is passive/intransitive (“to be saved”), so 돈 is the subject of “being saved.” Subjects take -이/가, giving 돈이 절약돼요 (“money is saved”).

Why does the sentence use 절약되다 (“to be saved”) instead of the active 절약하다 (“to save”)?

Korean often frames results impersonally. “돈을 절약하다” means “(I) save money” (active). “돈이 절약되다” means “money gets saved” (passive/stative). The latter emphasizes the result – money ends up saved by taking the bus.

Why is it 절약돼요 and not 절약되어요 or 절약되요?

This is a regular contraction: 되 + 어요 → 돼요. The full form 절약되어요 is grammatically correct but more formal/long. 절약돼요 is the common spoken contraction. 절약되요 is a spelling mistake—always use 돼요 for 되다 + 어요.

What tense and speech level is 절약돼요?

It’s present tense, polite form. The -요 ending makes it polite. So the sentence states a general truth or habitual result in polite speech.

Who is the implied subject in 버스를 타면 돈이 절약돼요?

Korean often omits obvious subjects. Here the implied subject of both clauses is “you” or “people in general.” So implicitly: “If you take the bus, (you) save money.”

Could you use 버스를 타서 돈이 절약돼요 instead? How would the nuance change?

Yes. -서 connects actions with a cause/result meaning “by doing X.”
• 버스를 타서 돈이 절약돼요 = “By taking the bus, money is saved.” (focus on method)
• 버스를 타면 돈이 절약돼요 = “If/when you take the bus, you save money.” (focus on condition/hypothesis)