Greetings
안녕하세요
An-nyeong-ha-se-yo
Hello (polite) — works any time of day. A slight bow comes naturally with it.
감사합니다
Gam-sa-ham-ni-da
Thank you (formal). 'Gomawoyo' is the casual version.
Daily life
네 / 아니요
Ne / A-ni-yo
Yes / No. 'Ne' also works as a polite 'I see / got it'.
얼마예요?
Eol-ma-ye-yo?
How much is it?
화장실 어디예요?
Hwa-jang-sil eo-di-ye-yo?
Where's the toilet?
Food
이거 주세요
I-geo ju-se-yo
I'll have this, please (point at the menu/item). '...juseyo' = please give me.
계산이요 / 계산서 주세요
Gye-san-i-yo
Check please — though you usually pay at the counter, not the table.
맛있어요
Ma-si-sseo-yo
It's delicious.
Social
괜찮아요
Gwaen-cha-na-yo
'It's OK / I'm fine / no thanks' — wildly versatile, used to accept or politely decline.
영어 할 수 있어요?
Yeong-eo hal su i-sseo-yo?
Do you speak English? (common among younger people and in central Seoul).
빨리빨리
Ppalli-ppalli
'Quickly, quickly' — the famous Korean fast-paced 'hurry' culture you'll feel everywhere.
Emergency
도와주세요!
Do-wa-ju-se-yo!
Help me! — for emergencies.