Verbseoul.
하다 verb
경고하다gyeonggohadato warn

To say to warn politely in the present tense, use 경고해요 (gyuhng-goh-hae-yoh). Below is the full conjugation of 경고하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
경고해
gyuhng-goh-hae
경고해요
gyuhng-goh-hae-yoh
경고합니다
gyuhng-goh-hahm-nee-dah
Past
경고했어
gyuhng-goh-hae-ssuh
경고했어요
gyuhng-goh-hae-ssuh-yoh
경고했습니다
gyuhng-goh-hae-sseum-nee-dah
Future
경고할 거야
gyuhng-goh-hahl- -guh-yah
경고할 거예요
gyuhng-goh-hahl- -guh-yae-yoh
경고할 겁니다
gyuhng-goh-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
경고하세요
gyuhng-goh-hah-sae-yoh
Suggestion / Let's Polite (요)
경고해요
gyuhng-goh-hae-yoh
Question Polite (요)
경고해요?
gyuhng-goh-hae-yoh-?
Connective “and” — (고)
경고하고
gyuhng-goh-hah-goh
Conditional “if” — (면)
경고하면
gyuhng-goh-hah-myuhn
Noun form — (기)
경고함
gyuhng-goh-hahm