IPA: /ˈkɛr.ləs.li/
KK: /ˈkɛr lɪs li/
In a way that shows a lack of attention or concern; done without careful thought.
He carelessly dropped the fragile vase, and it shattered on the floor.
Carelessly → It is formed from "care" (from Old English *caru*, meaning worry or concern) and "-less" (meaning without). The word "carelessly" means without care or concern.
Think of being 'without worry' ('-less') about something, which helps you remember that 'carelessly' means acting without care.