Verbseoul.
하다 verb
경계하다gyeonggyehadato be vigilant

To say to be vigilant politely in the present tense, use 경계해요 (gyuhng-gyae-hae-yoh). Below is the full conjugation of 경계하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
경계해
gyuhng-gyae-hae
경계해요
gyuhng-gyae-hae-yoh
경계합니다
gyuhng-gyae-hahm-nee-dah
Past
경계했어
gyuhng-gyae-hae-ssuh
경계했어요
gyuhng-gyae-hae-ssuh-yoh
경계했습니다
gyuhng-gyae-hae-sseum-nee-dah
Future
경계할 거야
gyuhng-gyae-hahl- -guh-yah
경계할 거예요
gyuhng-gyae-hahl- -guh-yae-yoh
경계할 겁니다
gyuhng-gyae-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
경계하세요
gyuhng-gyae-hah-sae-yoh
Suggestion / Let's Polite (요)
경계해요
gyuhng-gyae-hae-yoh
Question Polite (요)
경계해요?
gyuhng-gyae-hae-yoh-?
Connective “and” — (고)
경계하고
gyuhng-gyae-hah-goh
Conditional “if” — (면)
경계하면
gyuhng-gyae-hah-myuhn
Noun form — (기)
경계함
gyuhng-gyae-hahm