need not不用 means "(there's) no need to, don't have to" — it lifts an obligation. The classic trap: the negative of want / will / need要 ("need to") is need not不用, not don't不要 (which means "don't / don't want").
โครงสร้าง: Subject + 不用 + Verb Phrase
no need to不用worry担心。
No need to worry.
children孩子don't need to不用buy买a ticket票。
Children don't need to buy a ticket.
Remember: want / will / need要 ("need to") → need not不用 ("needn't"), NOT don't不要. need not不用 cancels a need; don't不要 is a prohibition ("don't"); cannot不能 = "can't"; not不should应该 = "shouldn't." Pick by which one you're denying.
ข้อควรระวัง
- You're welcome不用谢 ("you're welcome") is literally "no need to thank" — the same need not不用.