IPA: /ˈfɔːrθwɪθ/
KK: /ˈfɔrθwɪθ/
Without any delay; right away.
Please send me the report forthwith so I can review it.
Forthwith → It is formed from "forth" (from Old English "forð", meaning forward or out) and "with" (from Old English "wið", meaning against or with). The word "forthwith" means to do something immediately or without delay, indicating action taken forward or out right away.
Think of moving 'forward' ('forth') and doing something 'immediately' ('with') — that's why forthwith means to act right away.
No commonly confused words.