Verbseoul.
하다 verb (adj)
성실하다seongsilhadaconscientious

To say conscientious politely in the present tense, use 성실해요 (suhng-sheel-hae-yoh). Below is the full conjugation of 성실하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
성실해
suhng-sheel-hae
성실해요
suhng-sheel-hae-yoh
성실합니다
suhng-sheel-hahm-nee-dah
Past
성실했어
suhng-sheel-hae-ssuh
성실했어요
suhng-sheel-hae-ssuh-yoh
성실했습니다
suhng-sheel-hae-sseum-nee-dah
Future
성실할 거야
suhng-sheel-hahl- -guh-yah
성실할 거예요
suhng-sheel-hahl- -guh-yae-yoh
성실할 겁니다
suhng-sheel-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
성실하세요
suhng-sheel-hah-sae-yoh
Suggestion / Let's Polite (요)
성실해요
suhng-sheel-hae-yoh
Question Polite (요)
성실해요?
suhng-sheel-hae-yoh-?
Connective “and” — (고)
성실하고
suhng-sheel-hah-goh
Conditional “if” — (면)
성실하면
suhng-sheel-hah-myuhn
Noun form — (기)
성실함
suhng-sheel-hahm