Verbseoul.
하다 verb (adj)
멍청하다meongcheonghadafoolish, silly, stupid

To say foolish, silly, stupid politely in the present tense, use 멍청해요 (muhng-chuhng-hae-yoh). Below is the full conjugation of 멍청하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
멍청해
muhng-chuhng-hae
멍청해요
muhng-chuhng-hae-yoh
멍청합니다
muhng-chuhng-hahm-nee-dah
Past
멍청했어
muhng-chuhng-hae-ssuh
멍청했어요
muhng-chuhng-hae-ssuh-yoh
멍청했습니다
muhng-chuhng-hae-sseum-nee-dah
Future
멍청할 거야
muhng-chuhng-hahl- -guh-yah
멍청할 거예요
muhng-chuhng-hahl- -guh-yae-yoh
멍청할 겁니다
muhng-chuhng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
멍청하세요
muhng-chuhng-hah-sae-yoh
Suggestion / Let's Polite (요)
멍청해요
muhng-chuhng-hae-yoh
Question Polite (요)
멍청해요?
muhng-chuhng-hae-yoh-?
Connective “and” — (고)
멍청하고
muhng-chuhng-hah-goh
Conditional “if” — (면)
멍청하면
muhng-chuhng-hah-myuhn
Noun form — (기)
멍청함
muhng-chuhng-hahm