Learn Hardcore Korean: beoseuga jiyeondwaeyo.

In 버스가 지연돼요, 가 marks 버스 as the grammatical subject experiencing the action (being delayed). If you used 버스는 지연돼요, it would still be correct, but 는 turns 버스 into the topic and often adds a contrast or general‐topic nuance (“As for the bus, it’s delayed”). Using 가 simply presents “the bus” as the entity undergoing the delay without that extra contrast.

How is 지연돼요 constructed grammatically?

지연돼요 comes from the noun 지연 (delay) plus the verb 되다 (to become/to be). The base dictionary form is 지연되다 (“to be delayed”). To make it polite present tense, you attach -어요, but 지연 + 되 + 어요 contracts to 지연돼요.

Why is it spelled 돼요 with ㅐ rather than 되요 with ㅚ?

The verb stem 되- plus -어요 follows a contraction rule: 되 + 어요 → 돼요 (ㅚ + 어 contracts to ㅙ). Writing 되요 is nonstandard. Always use 돼요 in the polite present form of 되다.

What’s the difference between 지연돼요 and 늦어요?

지연되다 (“to be delayed”) is more formal/technical and used for scheduled public transport, events, flights, etc. 늦다 (“to be late”) is a general adjective/verb for people or things arriving late. Colloquially you might hear 버스가 늦어요, but 지연돼요 sounds more official, like an announcement.

How do I ask “Is the bus delayed?” in Korean?

You simply change the intonation to a question:
버스가 지연돼요?
For a more formal register, you can say 버스가 지연됩니까? (using -습니까).

What level of politeness is -요 here, and can I use other endings?

The -요 ending is the standard polite (informal‐polite) style you’d use with strangers or acquaintances.
• To sound more formal/public‐announcement style: 버스가 지연됩니다. (with -습니다)
• To sound casual/friendly: 버스가 지연돼. (drop 요)

How do I say “The bus was delayed” (past tense)?

Conjugate 지연되다 into polite past:
지연되다 → 지연되었어요 → 지연됐어요
So you say 버스가 지연됐어요.

Can I use 연기돼요 instead of 지연돼요?

연기되다 means “to postpone/reschedule” (usually performances or meetings). Buses and trains typically 지연되다 (“be delayed”). Saying 버스가 연기돼요 might be understood, but native speakers almost always use 지연돼요 for public transport.