Verbseoul.
하다 verb (adj)
무용하다muyonghadauseless

To say useless politely in the present tense, use 무용해요 (moo-yohng-hae-yoh). Below is the full conjugation of 무용하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
무용해
moo-yohng-hae
무용해요
moo-yohng-hae-yoh
무용합니다
moo-yohng-hahm-nee-dah
Past
무용했어
moo-yohng-hae-ssuh
무용했어요
moo-yohng-hae-ssuh-yoh
무용했습니다
moo-yohng-hae-sseum-nee-dah
Future
무용할 거야
moo-yohng-hahl- -guh-yah
무용할 거예요
moo-yohng-hahl- -guh-yae-yoh
무용할 겁니다
moo-yohng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
무용하세요
moo-yohng-hah-sae-yoh
Suggestion / Let's Polite (요)
무용해요
moo-yohng-hae-yoh
Question Polite (요)
무용해요?
moo-yohng-hae-yoh-?
Connective “and” — (고)
무용하고
moo-yohng-hah-goh
Conditional “if” — (면)
무용하면
moo-yohng-hah-myuhn
Noun form — (기)
무용함
moo-yohng-hahm