Learn Hardcore Korean: jeoneun oneul yaksogi isseoyo.

In Korean, -는/은 marks the topic (“as for …”), while -가/이 marks the grammatical subject. 저는 literally means “as for me,” framing the rest of the sentence as information about yourself. If you used 제가, it would be more emphatic (“it is I who …”) rather than neutral.

What does 있어요 mean here? Why doesn’t Korean have a separate verb for “to have”?

The verb 있다 literally means “to exist.” When a noun plus a subject marker precedes it (e.g. 약속이 있다), it expresses possession—“there is X” → “I have X.” So 약속이 있어요 is “An appointment exists (for me),” which we translate as “I have an appointment.” To say you don’t have something, use the opposite verb 없다 (e.g. 약속이 없어요 “I don’t have an appointment”).

Why is the subject marker -이 used on 약속 instead of -가?

Korean subject particles follow a simple rule: if a noun ends in a consonant, attach -이; if it ends in a vowel, attach -가. Because 약속 ends with the consonant ㄱ, it takes -이, becoming 약속이.

Why is there no particle after 오늘? Could I say 오늘에 instead?

Common time words like 오늘 (“today”), 내일 (“tomorrow”), 어제 (“yesterday”) act as adverbials and usually don’t need -에. You can technically say 오늘에, but in everyday speech Koreans almost always drop the -에.

What level of politeness is 있어요? How would I make it more formal or more casual?

The ending -어요 in 있어요 is polite informal style (해요체), suitable for most daily conversations.
• More formal (합쇼체): 저는 오늘 약속이 있습니다.
• More casual/intimate (해체): 오늘 약속 있어. (often dropping 저는 and using 나 instead of 저)

Can I drop 저는 and just say 오늘 약속이 있어요?

Yes. Korean often omits topics or subjects when they’re clear from context. In a chat about your plans, 오늘 약속이 있어요 is perfectly natural. You’d only include 저는 if you needed to clarify that it’s you (not someone else) or to contrast.

What’s the typical word order here? Could I say 약속이 오늘 있어요?

Standard Korean order is Topic/Subject → Time → Object/Subject → Verb. So 저는 (topic) + 오늘 (time) + 약속이 (subject) + 있어요 (verb). While 약속이 오늘 있어요 isn’t ungrammatical, placing the time word 오늘 before the noun or right before the verb feels much more natural.

What does 약속 cover? Does it only mean “appointment”?

약속 can mean “appointment,” “promise,” “date,” or “plan,” depending on context. When used with 있다, it generally refers to an arranged meeting or appointment. To talk about making or keeping a promise, you’d use verbs like 약속을 하다 (“to make a promise”) or 약속을 지키다 (“to keep a promise”).

How do I say the negative form, “I don’t have an appointment today”?

Simply change 있다 to its negative counterpart 없다:
저는 오늘 약속이 없어요.
This literally means “An appointment does not exist for me today.”