넌 나의 사랑 (neon na ee sarang) 넌 내 사랑이다 (neon nae sarang i da) but if you want to say "you are lovely" 넌 (optional) 사랑스러워 (neon sarang seu ro wo)

Korean say differently to someone. They can be older or younger than speaker. Or they are just friends or special mates. 너는 내 사랑(이야). Nuneun nae sarang(iya). 당신은 저의 사랑입니다.(사랑이에요) Dangsineun JuEui sarang imnida.(i-e-yo). Nu << Dangsin (polite way) Na << Ju (polite way)

Nonuen moesjin imnida... Im not quite sure because... Nonuen is you are and Nanuen is I'm :)