Verbseoul.
하다 verb (adj)
꿋꿋하다kkutkkuthadastrong

To say strong politely in the present tense, use 꿋꿋해요 (ggoot-ggoo-tae-yoh). Below is the full conjugation of 꿋꿋하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
꿋꿋해
ggoot-ggoo-tae
꿋꿋해요
ggoot-ggoo-tae-yoh
꿋꿋합니다
ggoot-ggoo-tahm-nee-dah
Past
꿋꿋했어
ggoot-ggoo-tae-ssuh
꿋꿋했어요
ggoot-ggoo-tae-ssuh-yoh
꿋꿋했습니다
ggoot-ggoo-tae-sseum-nee-dah
Future
꿋꿋할 거야
ggoot-ggoo-tahl- -guh-yah
꿋꿋할 거예요
ggoot-ggoo-tahl- -guh-yae-yoh
꿋꿋할 겁니다
ggoot-ggoo-tahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
꿋꿋하세요
ggoot-ggoo-tah-sae-yoh
Suggestion / Let's Polite (요)
꿋꿋해요
ggoot-ggoo-tae-yoh
Question Polite (요)
꿋꿋해요?
ggoot-ggoo-tae-yoh-?
Connective “and” — (고)
꿋꿋하고
ggoot-ggoo-tah-goh
Conditional “if” — (면)
꿋꿋하면
ggoot-ggoo-tah-myuhn
Noun form — (기)
꿋꿋함
ggoot-ggoo-tahm