Forthwith means immediately, without any delay at all. When a judge orders someone to appear in court forthwith, they mean right now, not tomorrow or next week. When a teacher tells students to stop talking forthwith, she wants instant silence.

The word has a formal, official feeling to it. You might hear it in courtrooms, legal documents, or serious announcements, but you probably wouldn't use it when chatting with friends. If your mom wants you to clean your room right away, she'd more likely say “immediately” or “right now” than “forthwith.”

When something must happen forthwith, there's no time for excuses, delays, or “I'll do it later.” The word carries weight and urgency, signaling that whatever needs to happen cannot wait another moment.