Learn Hardcore Korean: jeoneun jumare gyehoegi isseoyo.

가/이 are subject markers, used when you want to highlight or introduce a new subject.
If you said 제가 주말에 계획이 있어요, you’d be emphasizing “it’s me who has plans,” which feels more like a contrast or answer to a question.

What does 에 after 주말 indicate?

에 is a time particle. When attached to 주말 (“weekend”), 주말에 means “at/on the weekend.”

Use 에 for specific points in time (e.g. 아침에, 3시에, 내일에).
It tells you when the action or state (having plans) takes place.

Why is it 계획이 있어요 instead of 계획을 있어요 or just 계획 있어요?

Because 있다 is an existential/possession verb, not a transitive verb:

The thing that exists or that you have is the subject, so you mark it with 이/가.
계획이 있어요 literally means “Plans exist.”
You cannot use 을/를 here—that would imply you’re acting on the plans rather than having them.

What does 있어요 mean in this sentence?

Here, 있어요 comes from the verb 있다, which has two main uses:

“to exist” (there is/are)
“to have” (possession)
In 계획이 있어요, it means “I have (a) plan(s).”

Can I omit 저는 or rearrange the word order?

Yes. Korean often drops the topic if it’s clear from context. You could simply say 주말에 계획이 있어요 and still mean “I have plans this weekend.”

As for word order, the verb generally stays at the end, but you can move time or objects around for emphasis:
- 주말에 저는 계획이 있어요 (emphasizes “as for me”)
- 계획이 주말에 있어요 (emphasizes “it’s the plans that happen on the weekend”)

How would I say “I don’t have plans this weekend”?

Replace 있어요 with its negative 없어요:
저는 주말에 계획이 없어요.
This literally means “As for me, weekend + plans do not exist.”

How can I turn this into a question when asking someone else?

You have a few choices:

Drop the topic, use rising intonation:
주말에 계획이 있어요?
Use a slightly more polite ending:
주말에 계획 있으세요?
In very formal style, change the ending:
주말에 계획이 있으십니까?

Can I say 이번 주말에 계획이 있어요 instead of 주말에 계획이 있어요?

Absolutely. 이번 means “this,” so 이번 주말에 specifies “this coming weekend.” Without 이번, 주말에 could be interpreted more generally as “on weekends” or “on the weekend (in general).”

What’s the difference between 계획 and 약속 when talking about “plans”?

계획 refers to a plan, schedule, or intention you’ve made for yourself or in general (e.g. study plan, travel plan).
약속 means an appointment, promise, or engagement with someone else (e.g. meeting, date).
Use 계획 when you’re talking about your own agenda; use 약속 when you’ve committed to meet or do something with another person.

How would I say this in casual/informal speech?

Switch to the informal polite or plain form:

Drop 저는 (context is clear).
Use 있어 instead of 있어요.
You get: 주말에 계획 있어.
This is common among friends or in writing like texts/chats.