Verbseoul.
ㄹ stem
갈다galdato change, to replace, to switch (in general)

To say to change, to replace, to switch (in general) politely in the present tense, use 갈아요 (gah-rah-yoh). Below is the full conjugation of 갈다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
갈아
gah-rah
갈아요
gah-rah-yoh
갑니다
gahm-nee-dah
Past
갈았어
gah-rah-ssuh
갈았어요
gah-rah-ssuh-yoh
갈았습니다
gah-rah-sseum-nee-dah
Future
갈 거야
gahl- -guh-yah
갈 거예요
gahl- -guh-yae-yoh
갈 겁니다
gahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
가세요
gah-sae-yoh
Suggestion / Let's Polite (요)
갈아요
gah-rah-yoh
Question Polite (요)
갈아요?
gah-rah-yoh-?
Connective “and” — (고)
갈고
gahl-goh
Conditional “if” — (면)
갈면
gahl-myuhn
Noun form — (기)
gahm