바뀌다([ba-kkwi-da/change]) means to change, to be changed - intransitive. In polite speech, say 바뀌어요([ba-kkwi-eo-yo]) or 바뀝니다([ba-kkwi-m-ni-da]). Very common for schedule, plan, or situation change.
바뀌었어요([ba-kkwi-eo-sseo-yo/changed]) is the polite past form. Example: 계획이 바뀌었어요 (The plan changed) - very natural EPS-TOPIK sentence.
바뀌어야 해요([ba-kkwi-eo-ya hae-yo/have to change]) expresses obligation. Example: 일정이 바뀌어야 해요 → 바뀌어야 해요 (Have to change the schedule) - essential EPS-TOPIK expression.
바뀌다([ba-kkwi-da/change]) means "to change" - intransitive, situation or plan changes by itself. Different from 바꾸다 (to change something actively).
바뀌다 is intransitive: 계획이 바뀌었어요 (The plan changed by itself)
바꾸다 is transitive: 계획을 바꿨어요 (I changed the plan actively) - This difference is tested in EPS-TOPIK.
1. Schedule: “일정이 바뀌어요 (il-jeong-i ba-kkwi-eo-yo)” The schedule changes
2. Past: 바뀌었어요([ba-kkwi-eo-sseo-yo/changed]) - 계획이 바뀌었어요, 어제 바뀌었어요
3. Wish: 바뀌고 싶어요([ba-kkwi-go si-peo-yo/want to change]) - 분위기가 바뀌고 싶어요.
4. Must: 비밀번호가 바뀌어야 해요([ba-kkwi-eo-ya hae-yo/have to change]) - Must change for safety.
A: Does the schedule change?
B: 네, 일정이 바뀌어요. B: ne, il-jeong-i ba-kkwi-eo-yo.B: Yes, the schedule changes. - 바뀌다([ba-kkwi-da/change])
A: Did the plan change?
B: 네, 계획이 바뀌었어요. B: ne, gye-hoek-i ba-kkwi-eo-sseo-yo.B: Yes, the plan changed.
A: 언제 바뀌었어요? A: eon-je ba-kkwi-eo-sseo-yo?A: When did it change?
B: 어제 바뀌었어요. B: eo-je ba-kkwi-eo-sseo-yo.B: It changed yesterday. - 바뀌었어요([ba-kkwi-eo-sseo-yo/changed])
A: When does it have to change?
B: 내일까지 바뀌어야 해요. B: nae-il-kka-ji ba-kkwi-eo-ya hae-yo.B: It has to change by tomorrow.
A: 뭐가 바뀌어야 해요? A: mwo-ga ba-kkwi-eo-ya hae-yo?A: What has to change?
B: 비밀번호가 바뀌어야 해요. B: bi-mil-beon-ho-ga ba-kkwi-eo-ya hae-yo.B: The password has to change. - 바뀌어야 해요([ba-kkwi-eo-ya hae-yo/have to change])
• 바뀌다([ba-kkwi-da/change]) change (intransitive)
- 바뀌었어요([ba-kkwi-eo-sseo-yo/changed]) changed
- 바뀌고 싶어요([ba-kkwi-go si-peo-yo/want to change]) want to change
- 바뀌어야 해요([ba-kkwi-eo-ya hae-yo/have to change]) have to change
- 바뀌지 마세요([ba-kkwi-ji ma-se-yo/don't change]) don't change