Learn Hardcore Korean: eojjeomyeon oneul gichaga neujeuljido mollayo.

어쩌면 is an adverb meaning “perhaps” or “maybe.” It’s used to introduce a speculation or possibility before the main clause. Placing it at the beginning signals that what follows is not certain, just a guess.

What is the grammatical structure -을지도 몰라요?

Breakdown of -을지도 몰라요:

-을지: a suffix adding uncertainty to a verb/adjective stem (for stems ending in a consonant; use -ㄹ지 after a vowel).
-도: an emphatic particle here reinforcing “even that.”
모르다: “to not know.”
When combined, -을지도 모르다 literally means “one doesn’t know if (something will happen),” but idiomatically it becomes “might,” “may,” or “could.” In polite present it’s -을지도 몰라요.

Why is 늦다 changed to 늦을 before 지도 몰라요, and not 늦지도 몰라요?

You need to attach -을지 to the verb stem:
• Verb stem of 늦다 is 늦- (ends in a consonant), so you add -을, giving 늦을.
• Then add -지, -도, and 모르다 → 늦을지도 몰라요.
If you said 늦지도 몰라요, that would use 늦다 + -지 몰라요 (“might not be late”), which reverses the meaning.

Why do we use 몰라요 here if we’re talking about what might happen, not about “not knowing”?

In the idiom -지도 모르다, 모르다 has lost its literal “not know” meaning and simply marks uncertainty. Think of -을지도 모르다 as one fixed grammar chunk: “might,” “could,” “may.”

Why is the subject marked with 가 in 기차가, not 는?

-가 is the subject marker, often introducing new or neutral information. Using -는 would topicalize or contrast “the train” against something else (“As for the train, …”), which changes the nuance. Here, 기차가 simply presents the train as the thing that might be late.

Can we replace -을지도 몰라요 with -ㄹ 수도 있어요? Are they the same?

Both express possibility, but subtle differences exist:
• -을지도 몰라요 feels slightly more tentative or speculative.
• -ㄹ 수도 있어요 is a bit more neutral, literally “there’s the possibility that….”
In many cases you can swap them without a big change:
오늘 기차가 늦을지도 몰라요 → 오늘 기차가 늦을 수도 있어요.

What about -을지도 몰라요 versus -을 것 같아요?

• -을지도 몰라요 is hypothetical uncertainty (“it might”).
• -을 것 같아요 describes a guess based on some clues or feeling (“it seems like”).
Use -을지도 몰라요 when you’re simply speculating; use -을 것 같아요 when you have some reason or evidence for your guess.