Verbseoul.
하다 verb (adj)
불가능하다bulganeunghadato be impossible

To say to be impossible politely in the present tense, use 불가능해요 (bool-gah-neung-hae-yoh). Below is the full conjugation of 불가능하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
불가능해
bool-gah-neung-hae
불가능해요
bool-gah-neung-hae-yoh
불가능합니다
bool-gah-neung-hahm-nee-dah
Past
불가능했어
bool-gah-neung-hae-ssuh
불가능했어요
bool-gah-neung-hae-ssuh-yoh
불가능했습니다
bool-gah-neung-hae-sseum-nee-dah
Future
불가능할 거야
bool-gah-neung-hahl- -guh-yah
불가능할 거예요
bool-gah-neung-hahl- -guh-yae-yoh
불가능할 겁니다
bool-gah-neung-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
불가능하세요
bool-gah-neung-hah-sae-yoh
Suggestion / Let's Polite (요)
불가능해요
bool-gah-neung-hae-yoh
Question Polite (요)
불가능해요?
bool-gah-neung-hae-yoh-?
Connective “and” — (고)
불가능하고
bool-gah-neung-hah-goh
Conditional “if” — (면)
불가능하면
bool-gah-neung-hah-myuhn
Noun form — (기)
불가능함
bool-gah-neung-hahm