Verbseoul.
하다 verb (adj)
건전하다geonjeonhadato be sound, wholesome (in terms of having upright ethics)

To say to be sound, wholesome (in terms of having upright ethics) politely in the present tense, use 건전해요 (guhn-chuhn-hae-yoh). Below is the full conjugation of 건전하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
건전해
guhn-chuhn-hae
건전해요
guhn-chuhn-hae-yoh
건전합니다
guhn-chuhn-hahm-nee-dah
Past
건전했어
guhn-chuhn-hae-ssuh
건전했어요
guhn-chuhn-hae-ssuh-yoh
건전했습니다
guhn-chuhn-hae-sseum-nee-dah
Future
건전할 거야
guhn-chuhn-hahl- -guh-yah
건전할 거예요
guhn-chuhn-hahl- -guh-yae-yoh
건전할 겁니다
guhn-chuhn-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
건전하세요
guhn-chuhn-hah-sae-yoh
Suggestion / Let's Polite (요)
건전해요
guhn-chuhn-hae-yoh
Question Polite (요)
건전해요?
guhn-chuhn-hae-yoh-?
Connective “and” — (고)
건전하고
guhn-chuhn-hah-goh
Conditional “if” — (면)
건전하면
guhn-chuhn-hah-myuhn
Noun form — (기)
건전함
guhn-chuhn-hahm