Verbseoul.
descriptive
얇다yaldathin (of something flat, like a book or a slice of meat)

To say thin (of something flat, like a book or a slice of meat) politely in the present tense, use 얇아요 (yahl-ah-yoh). Below is the full conjugation of 얇다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
얇아
yahl-ah
얇아요
yahl-ah-yoh
얇습니다
yahl-seum-nee-dah
Past
얇았어
yahl-ah-ssuh
얇았어요
yahl-ah-ssuh-yoh
얇았습니다
yahl-ah-sseum-nee-dah
Future
얇을 거야
yahl-eul- -guh-yah
얇을 거예요
yahl-eul- -guh-yae-yoh
얇을 겁니다
yahl-eul- -guhm-nee-dah

Other useful forms

Command Polite (세요)
얇으세요
yahl-eu-sae-yoh
Suggestion / Let's Polite (요)
얇아요
yahl-ah-yoh
Question Polite (요)
얇아요?
yahl-ah-yoh-?
Connective “and” — (고)
얇고
yahl-goh
Conditional “if” — (면)
얇으면
yahl-eu-myuhn
Noun form — (기)
얇음
yahl-eum