Verbseoul.
regular
나빠지다nappajidato get worse, to deteriorate

To say to get worse, to deteriorate politely in the present tense, use 나빠져요 (nah-bbah-chyuh-yoh). Below is the full conjugation of 나빠지다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
나빠져
nah-bbah-chyuh
나빠져요
nah-bbah-chyuh-yoh
나빠집니다
nah-bbah-cheem-nee-dah
Past
나빠졌어
nah-bbah-chyuh-ssuh
나빠졌어요
nah-bbah-chyuh-ssuh-yoh
나빠졌습니다
nah-bbah-chyuh-sseum-nee-dah
Future
나빠질 거야
nah-bbah-cheel- -guh-yah
나빠질 거예요
nah-bbah-cheel- -guh-yae-yoh
나빠질 겁니다
nah-bbah-cheel- -guhm-nee-dah

Other useful forms

Command Polite (세요)
나빠지세요
nah-bbah-chee-sae-yoh
Suggestion / Let's Polite (요)
나빠져요
nah-bbah-chyuh-yoh
Question Polite (요)
나빠져요?
nah-bbah-chyuh-yoh-?
Connective “and” — (고)
나빠지고
nah-bbah-chee-goh
Conditional “if” — (면)
나빠지면
nah-bbah-chee-myuhn
Noun form — (기)
나빠짐
nah-bbah-cheem