Verbseoul.
하다 verb (adj)
심각하다simgakhadato be severe, profound

To say to be severe, profound politely in the present tense, use 심각해요 (sheem-gah-kae-yoh). Below is the full conjugation of 심각하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
심각해
sheem-gah-kae
심각해요
sheem-gah-kae-yoh
심각합니다
sheem-gah-kahm-nee-dah
Past
심각했어
sheem-gah-kae-ssuh
심각했어요
sheem-gah-kae-ssuh-yoh
심각했습니다
sheem-gah-kae-sseum-nee-dah
Future
심각할 거야
sheem-gah-kahl- -guh-yah
심각할 거예요
sheem-gah-kahl- -guh-yae-yoh
심각할 겁니다
sheem-gah-kahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
심각하세요
sheem-gah-kah-sae-yoh
Suggestion / Let's Polite (요)
심각해요
sheem-gah-kae-yoh
Question Polite (요)
심각해요?
sheem-gah-kae-yoh-?
Connective “and” — (고)
심각하고
sheem-gah-kah-goh
Conditional “if” — (면)
심각하면
sheem-gah-kah-myuhn
Noun form — (기)
심각함
sheem-gah-kahm