Verbseoul.
하다 verb (adj)
흔하다heunhadato be frequent, to be common

To say to be frequent, to be common politely in the present tense, use 흔해요 (heun-hae-yoh). Below is the full conjugation of 흔하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
흔해
heun-hae
흔해요
heun-hae-yoh
흔합니다
heun-hahm-nee-dah
Past
흔했어
heun-hae-ssuh
흔했어요
heun-hae-ssuh-yoh
흔했습니다
heun-hae-sseum-nee-dah
Future
흔할 거야
heun-hahl- -guh-yah
흔할 거예요
heun-hahl- -guh-yae-yoh
흔할 겁니다
heun-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
흔하세요
heun-hah-sae-yoh
Suggestion / Let's Polite (요)
흔해요
heun-hae-yoh
Question Polite (요)
흔해요?
heun-hae-yoh-?
Connective “and” — (고)
흔하고
heun-hah-goh
Conditional “if” — (면)
흔하면
heun-hah-myuhn
Noun form — (기)
흔함
heun-hahm