Verbseoul.
regular
막다makdato stop up

To say to stop up politely in the present tense, use 막아요 (mah-gah-yoh). Below is the full conjugation of 막다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
막아
mah-gah
막아요
mah-gah-yoh
막습니다
mahg-sseum-nee-dah
Past
막았어
mah-gah-ssuh
막았어요
mah-gah-ssuh-yoh
막았습니다
mah-gah-sseum-nee-dah
Future
막을 거야
mah-geul- -guh-yah
막을 거예요
mah-geul- -guh-yae-yoh
막을 겁니다
mah-geul- -guhm-nee-dah

Other useful forms

Command Polite (세요)
막으세요
mah-geu-sae-yoh
Suggestion / Let's Polite (요)
막아요
mah-gah-yoh
Question Polite (요)
막아요?
mah-gah-yoh-?
Connective “and” — (고)
막고
mahg-ggoh
Conditional “if” — (면)
막으면
mah-geu-myuhn
Noun form — (기)
막음
mah-geum