Verbseoul.
하다 verb
상하다sanghadato go bad (sour, rotten), to get stale

To say to go bad (sour, rotten), to get stale politely in the present tense, use 상해요 (sahng-hae-yoh). Below is the full conjugation of 상하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
상해
sahng-hae
상해요
sahng-hae-yoh
상합니다
sahng-hahm-nee-dah
Past
상했어
sahng-hae-ssuh
상했어요
sahng-hae-ssuh-yoh
상했습니다
sahng-hae-sseum-nee-dah
Future
상할 거야
sahng-hahl- -guh-yah
상할 거예요
sahng-hahl- -guh-yae-yoh
상할 겁니다
sahng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
상하세요
sahng-hah-sae-yoh
Suggestion / Let's Polite (요)
상해요
sahng-hae-yoh
Question Polite (요)
상해요?
sahng-hae-yoh-?
Connective “and” — (고)
상하고
sahng-hah-goh
Conditional “if” — (면)
상하면
sahng-hah-myuhn
Noun form — (기)
상함
sahng-hahm