The particle -만 can be attached to nouns to mean just that noun, or only that noun. It replaces any subject or object marking particles that may be attached to the noun.
Let’s see an example:
너를 좋아해. = “I like you.”
너 = you
-를 is the object marking particle
But now look at this:
너만 좋아해. = “I only like you.”
The particle -만 has replaced -를 and context will have to make it clear that 너 is the object of the sentence.
-만 is usually used with nouns, but can also be attached in the middle of the grammatical principle -아야 하다 / -어야 하다, which means “to have to do X”. The final construction looks like this: -아야만 하다 / -어야만 하다 and means “to just have to do X”. Check out the example below from Make It Right.
It can also be added to other grammatical principles. Check out the examples below from J’amais Vu and DNA.
Burn It (feat. MAX) by Agust D
재만 남을지도 모르지 ~ “I’m not sure if only ash would be left…”
Noun: 재 – ash
Make It Right
내가 날 눈치챘던 순간 떠나야만 했어. ~ I just had to leave the moment you noticed me.
Original verb: 따나다 – to leave
오직 내게만 남겨질 그 memory. ~ “…that memory left behind only for me.”
Original noun: 내 – me + -에게 – to/for
귓가엔 느린 심장 소리귓가엔 느린 심장 소리만. ~ “Nothing but the slow sound of my heartbeat in my ears.”
Original noun: 소리 – sound
시차 (My Time)
왜 나만 다른 시공간 속인 걸까? ~ “Why am I the only one in a different space-time?”
Original noun: 나 – I, me
아니 조금만 쉬면 어때? ~ “No, how about resting just a little?”
Original noun: 조금 – a little bit
이런 게 말로만 듣던 사랑이란 감정일까? ~ “…that this is the emotion called ‘love’ that I’ve only ever heard about?”
Literal translation – “…that I’ve only ever heard about via words?”
Original noun: 말 – words + -로 – via
우리들 미래는 기쁨만 ~ “Our future is only happiness.”
Original noun: 기쁨 – happiness, gladness