Verbseoul.
하다 verb (adj)
성대하다seongdaehadagrand

To say grand politely in the present tense, use 성대해요 (suhng-dae-hae-yoh). Below is the full conjugation of 성대하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
성대해
suhng-dae-hae
성대해요
suhng-dae-hae-yoh
성대합니다
suhng-dae-hahm-nee-dah
Past
성대했어
suhng-dae-hae-ssuh
성대했어요
suhng-dae-hae-ssuh-yoh
성대했습니다
suhng-dae-hae-sseum-nee-dah
Future
성대할 거야
suhng-dae-hahl- -guh-yah
성대할 거예요
suhng-dae-hahl- -guh-yae-yoh
성대할 겁니다
suhng-dae-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
성대하세요
suhng-dae-hah-sae-yoh
Suggestion / Let's Polite (요)
성대해요
suhng-dae-hae-yoh
Question Polite (요)
성대해요?
suhng-dae-hae-yoh-?
Connective “and” — (고)
성대하고
suhng-dae-hah-goh
Conditional “if” — (면)
성대하면
suhng-dae-hah-myuhn
Noun form — (기)
성대함
suhng-dae-hahm