Verbseoul.
하다 verb (adj)
충실하다chungsilhadafaithful

To say faithful politely in the present tense, use 충실해요 (choong-sheel-hae-yoh). Below is the full conjugation of 충실하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
충실해
choong-sheel-hae
충실해요
choong-sheel-hae-yoh
충실합니다
choong-sheel-hahm-nee-dah
Past
충실했어
choong-sheel-hae-ssuh
충실했어요
choong-sheel-hae-ssuh-yoh
충실했습니다
choong-sheel-hae-sseum-nee-dah
Future
충실할 거야
choong-sheel-hahl- -guh-yah
충실할 거예요
choong-sheel-hahl- -guh-yae-yoh
충실할 겁니다
choong-sheel-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
충실하세요
choong-sheel-hah-sae-yoh
Suggestion / Let's Polite (요)
충실해요
choong-sheel-hae-yoh
Question Polite (요)
충실해요?
choong-sheel-hae-yoh-?
Connective “and” — (고)
충실하고
choong-sheel-hah-goh
Conditional “if” — (면)
충실하면
choong-sheel-hah-myuhn
Noun form — (기)
충실함
choong-sheel-hahm